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According to Merriam-Webster, to throttle means to regulate the speed via a constricting valve, especially to speed down.

For example, "to regulate and especially to reduce the speed of (something, such as an engine) by such means".

When someone says, throttle this, in my experience they mean, restrict it, slow it.

So "full throttle" to me, would mean "to slow down as much as possible", "to fully restrict".

But it seems it means the opposite, "maximum speed".

Can anyone explain to me this contradction?

Juan Perez
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    Originally, *throttle* meant *throat. So "full-throttle" for a motorized vehicle is like a lion's full-throated roar* - the throttle/throat is opened as wide as possible (for maximum throughput of fuel or air). It's just that the verb *to throttle* came to have the meaning *choke* (fatally cut off someone's air by squeezing their throat), which led to "throttling back" meaning "reduce the fuel supply" to a vehicle's engine. – FumbleFingers Dec 19 '23 at 16:11
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    "Throttle" in this usage is synonymous with "accelerator". It's the name of the control, not what it does. It's dated though, because modern cars don't have carburettors or throttles. – Weather Vane Dec 19 '23 at 17:18
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    @WeatherVane And let's not even get into chokes. – user888379 Dec 19 '23 at 17:24
  • @user888379 or advance/retard. – Weather Vane Dec 19 '23 at 17:26
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    Already covered in... https://mechanics.stackexchange.com/a/83158/6299 https://ell.stackexchange.com/q/169310/4376 and https://ell.stackexchange.com/q/213233/4376 – Chenmunka Dec 19 '23 at 17:34
  • @WeatherVane, your comment seems to be the answer; why not post it such? – jsw29 Dec 19 '23 at 23:56
  • There's an implied word missed out "fully OPEN throttle" – Criggie Dec 20 '23 at 00:36
  • We do also say "full bore". – mckenzm Dec 20 '23 at 04:42
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    And used in a sentence: I hit full throttle to drive faster on the parkway, and then throttled back to park on the driveway. – Douglas Wiley Dec 20 '23 at 13:52
  • Reminds me of some refrigerator controls. 'Turn the cold up' – Lamar Latrell Dec 20 '23 at 21:25
  • @weathervane Carburetors are still found in many motorcycles and power tools as well. – barbecue Dec 20 '23 at 23:34
  • @WeatherVane Even fuel injected gasoline engines have a throttle. The thing it lives in is a "throttle body" since fuel injection replaced carburetors. – BenjiWiebe Dec 21 '23 at 01:08
  • @FumbleFingers, re '"throttling back" meaning "reduce the fuel supply"': actually it means reducing the air flow. So it is consistent with the general meaning of "throttle". The amount of fuel is reduced as a side effect to keep the mixture right. (So strictly speaking, the "gas pedal" should be called the "air pedal".) – prl Dec 21 '23 at 22:36
  • Can you Post instances of real, published English? Either way I think you'd get better help in English Language Learners.

    Merriam-Webster speaks of language in general, not specifically engines or speed.

    'To throttle' means to regulate speed but 'to speed down' won't work in English. That would need 'reduce speed…' or 'slow/throttle down…'

    You yourself said what matters: to 'fully throttle' might mean 'to slow down…' or ' fully restrict' but 'full throttle' is the opposite.

    Again, I think you'd get better help in English Language Learners.

     – Robbie Goodwin Dec 23 '23 at 00:01

6 Answers6

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Full throttle or wide open throttle means the throttle is fully open, allowing as much air and fuel as possible to the engine, and hence producing as much power as possible. (Wikipedia: Wide open throttle.) It's like a door. If it's wide open, lots of people can go through, if it's nearly closed it's hard to get anything through.

To throttle means to regulate power using a throttle, usually but not always by partially closing the throttle and reducing the amount of air and fuel reaching the engine. (Wikipedia: Throttle). If you think of full throttle as the default state, then any change to the throttle will be to reduce power. You can throttle up or throttle down to increase or decrease the flow to the engine and hence often increase or decrease the speed: (See this question about "throttle up".)

Stuart F
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  • There are plenty of similar derived terms, the meaning of which should now be obvious (@JuanPerez) : to throttle back or close the throttle is to reduce the opening and therefore flow, to open the throttle is to increase it. – Chris H Dec 20 '23 at 09:22
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    +1 this is a great answer. It would be even better with identification of the difference between throttle, n. and throttle, v. This would clear up a great number of comments elsewhere along the lines of, English is sooo messed up, and so on. to march, v. and March, n. (between February and April) have entirely separate meanings, and we don't generally sit around and lament about this. – Stephan Samuel Dec 20 '23 at 15:44
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    It seems like you've fleshed out the question well, as opposed to providing an answer. – Lamar Latrell Dec 20 '23 at 21:26
  • This is the best answer. Anyone familiar with the throttle body of a gas engine knows how it works -- something people seem to know less about today. "Full throttle" is short for "open(ed) full throttle", which is a fully-open throttle body... – Dúthomhas Dec 21 '23 at 00:17
  • @LamarLatrell What doesn't answer the question? If you don't know what a throttle is, it does sound goofy. Stuart explained the etymology and how it makes sense. – Azor Ahai -him- Dec 21 '23 at 02:29
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    Knowing what a throttle is, it still sounds goofy. It's like we've kicked the can down the road (fleshed out the question), I guess I'm still interested why people didn't predict the confusion in the first place. – Lamar Latrell Dec 21 '23 at 07:47
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    @StephanSamuel but March the month and march the activity have different etymologies: despite being associated with martial discipline, marching is related to marking. Throttle the verb comes directly from throttle the noun, so the apparent contradiction in meaning is not so easily dismissed. – phoog Dec 21 '23 at 11:32
  • @LamarLatrell I think it's a bit antiquated now, but a phrase I've heard used is "open the throttle" (or something like "open 'er up".) Back when people who operated vehicles would tend to understand how they worked, there wouldn't have been much confusion. But as controls became more abstract, the word seems to have become disconnected from its origin. – JimmyJames Dec 21 '23 at 16:49
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    I don't find "think of full throttle as the default state" at all intuitive - as Neil_UK points out, if you don't press the pedal in a car, you get a closed throttle. To go to "full throttle" is always an explicit act, requiring you to fully push down on the pedal (or fully shift a lever on a motorbike, etc). – IMSoP Dec 21 '23 at 17:05
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    It seems to me that a throttle is fully throttled in its base state and the action of operating it unthrottles the system. As silly as it sounds personally I think 'full unthrottle' makes more sense. As I've mentioned it's a bit like refrigerator controls, or bad GUI design where you click an UI element on to turn something off. – Lamar Latrell Dec 21 '23 at 18:20
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    @phoog just as well but how easily the etymology-derived contradiction is dismissed or not doesn't clear up the OP's contradiction dilemma. In fact, the etymology merely confuses, evidenced by the fact that there is disagreement here on the meaning of the ultimate extent of the verb. This answer hints at the simple fact that n. and v., throttle, mean different things, substantially in common use at least, wherever the words come from. – Stephan Samuel Dec 21 '23 at 18:56
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    @LamarLatrell Who's "people"? Nobody out there carefully considers what an idiom is going to sound like in less context decades later when they coin it. – Azor Ahai -him- Dec 22 '23 at 03:19
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    The people coining the technical terminology in the first place. If it's an idiom for you maybe that goes some way to explain why you're not seeing things the same way. – Lamar Latrell Dec 22 '23 at 05:52
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    When we talk about throttling an internet connection, it always refers to reduction in speed because we expect that network connections always run at full speed unless prevented from doing so. But engines we expect to always be in a managed state, so "full throttle" is different from the norm. – Darth Pseudonym Dec 22 '23 at 16:37
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    @LamarLatrell I don't think anyone sat down and decided what "full throttle" should mean. Rather, there were a series of steps where the meaning shifted slightly, until it had almost flipped. This is actually surprisingly common - look up the history of the word "nice", for instance! – IMSoP Dec 22 '23 at 17:07
  • @DarthPseudonym's comment may be hinting at a possible explanation of the apparent contradiction: it may be that the noun and the verb have their respective origins in describing different kinds of devices. The noun seems to be mostly used in describing the devices for which being closed is the default state, and then something needs to be done to open them, while the verb is used for the devices for which being fully opened is the default state and then something needs to be done to reduce their openness. – jsw29 Dec 22 '23 at 23:44
  • @IMSoP well that etymology, if you had the details, would make a great answer ✅. – Lamar Latrell Dec 23 '23 at 04:38
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To quote Neil, 'This illustrates [a typical] case where the meaning of language subtly shifts over decades of usage.'

The Online Etymological Dictionary gives the sequencing of the appearance of each usage in the English lexis [reformatted and otherwise adjusted slightly here]:

  • throat (n.): Old English [pre Norman Conquest] þrote

  • throat (v.) was used in the late 14c. to mean "cut the throat of, kill by cutting the throat"

  • throttle (v.): "strangle to death," c. 1400, probably from Middle English throte "throat" (see throat) + -le [possibly just to distinguish it from the preceding verb]

  • throttle (n.) 1540s, "throat;" it appears to be an independent formation from throat, perhaps a diminutive form, not derived directly from the verb. The mechanical sense is first recorded 1872, short for throttle-valve (1824). Full-throttle (allowing maximum speed) is from 1848 in reference to steam engines.

So the verb always had the strangulation sense, while the noun merely refers (literally, but most often figuratively) just to an actual throat, more broadly an orifice, with no reference to constriction/restriction. So throttle back retains the sense of constriction/limitation the verb has, while at full throttle with the noun means with fully open throttle.

Edwin Ashworth
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    Throttle valves of the slide type predate Watts by at least fifty years. I'm also looking into sluice gates for waterwheels. These are termed throttles today, but I haven't found pre 1770 example yet. See patents filed in 1771 and 1772 for slide valve throttles. – Phil Sweet Dec 20 '23 at 14:07
  • I mean... in a way, strangulation is diminutive to outright slitting the throat – No Name Dec 21 '23 at 01:03
  • I think this is right idea. There’s throttle — noun/the throat—of which you can have full use of: full throat/full throttle. And then there’s throttle — verb/to offend the throat. – Tinfoil Hat Dec 21 '23 at 02:05
  • @TinfoilHat I disagree. The body part throttle is the narrowest part of the passage. It is also the part which can be closed at will. It is no coincidence that this body part is used as the name for technical mechanisms which restrict a flow, and that the verb throttle is a synonym for "restrict a flow"; originally the air flow through the wind pipe, and later all kinds of flows. The throttle is also in the middle, which distinguishes it from mouth or gate or outlet. – Peter - Reinstate Monica Dec 22 '23 at 17:01
  • @Peter-ReinstateMonica — Full throttle means full throat — which is your “narrow passage” unrestricted. – Tinfoil Hat Dec 23 '23 at 00:05
  • @TinfoilHat Natural language is not fully logical, which is part of the fun. It may indeed be short for "fully open" or "fully down" (for a gas pedal or other control lever). That dictionary entry is actually pretty illuminating: "1. a valve for regulating the supply of a fluid (such as steam) to an engine; 2. Throat". The throat is the air flow valve in the body. – Peter - Reinstate Monica Dec 23 '23 at 03:41
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This illustrates the case where the meaning of language subtly shifts over decades of usage.

Let's start with the verb 'to throttle', meaning restrict. This action was needed to control the speed of internal combustion engines, to control the speed, by 'throttling' the supply of air and fuel to it.

When the person using the term is designing the car, or mending the engine, it's this verb form that's uppermost in their mind.

To the user of the car, not needing to know any of the details of an engine, sitting facing a range of controls (the brake, the clutch, the throttle), throttle is a noun, the name of the control.

The default state of a car is the engine running at idle. To make it do something useful, you have to 'give it some throttle'. To make it go as fast as it can, you give it 'full throttle'.

This is reinforced by the fact that, in a car, you have a choice between two pedals. You have the brake, which slows the car down, and the throttle, which obviously does the opposite thing.

Concentrating on the throttle pedal, it is spring-loaded in the low-speed direction. To make the car go faster, you press harder on the throttle, you give it more throttle.

The original verb form retains its sense of operation direction. The noun form appears to have lost that sense. When we say 'throttle it up', we are not even using the original verb form, but a new verb based on the noun, use the throttle control to so as to increase the speed.

Neil_UK
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  • Do Brits really call the accelerator the "throttle"? I mean, I know you wouldn't call it the "gas", because you call it petrol, but... – No Name Dec 21 '23 at 00:59
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    I think "accelerator" is more common, but "throttle" is reasonably widely used, in my experience. Yes, even on electric cars, just as we use "dial" to enter a number on a push-button telephone. – Toby Speight Dec 21 '23 at 09:40
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    The noun is the original word, not the verb. – phoog Dec 21 '23 at 11:38
  • @TobySpeight And with electric cars, I'm sure people will continue to say 'hit the gas' in the US and Canada, – JimmyJames Dec 21 '23 at 16:54
  • The use of "throttle" to designate a control used by a machine's operator is, I believe, near-ubiquitous when it is a hand control, as in airplanes, boats, locomotives and lawnmowers. In these cases, it is used even when the engine being controlled is a diesel or a gas turbine, where control is effected by altering the fuel flow rather than that of the working fluid, and it is also sometimes used where the device being controlled is an electric motor. – sdenham Dec 21 '23 at 18:00
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This is my first go at this (as a native British English speaker)! I'm not a linguist either and my school days were many decades ago but here goes...

You say "Throttle is to slow down, but full throttle is max speed?" Well, by the first word, "Throttle", you are referring to the verb "to throttle" which means to restrict in some way. We're all in agreement there I think?

"full throttle" refers to an adjective and a noun, which, from the days of early petrol engines, forms a part of the carburettor (the Venturi and the butterfly valve). The butterfly valve, connected by a cable to the accelerator pedal, when fully open, allows maximum air into the carb. which mixes with more petrol which produces more power. So "full throttle" became an abbreviation of "a fully open throttle".

So it is essentially the difference between using the word as a verb and as a noun. The verb is as you expect. The noun, because it became an actual component of an engine, is treated differently due to the associated butterfly valve.

user33214
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To throttle means to reduce the diameter of, to restrict. Thus, we even say “I was so upset, I could have throttled him,” where throttle means to strangle (reduce the effective diameter of his windpipe)… obviously used figuratively in that context.

The throttle on an engine is a valve or mechanism for controlling the fuel supplied. Thus full throttle means with the supply wide open, so with no restriction. And to throttle back means to reduce the fuel flow, and thus the power, speed, or (metaphorically) the intensity of a thing. It should be heard as meaning to adjust the throttle in the direction of reduced throughput, and in that sense is analogous to dial back: both throttles and dials can be used to either increase or decrease a quantity, so the adverb back means in the direction to decrease the quantity.

In any event, though we might wish that languages were 100% rational and consistent, they aren’t. Consider that Get up from that chair! and Get down from that chair! both mean stand up (with different connotations, to be sure). If English were consistent, we might expect throttle not to mean strangle. But then we might not expect kneecap to mean break someone’s kneecaps either.

PaulTanenbaum
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  • There are all sorts of uses you don't address. throttle back/down for engines, for example. – Lambie Dec 19 '23 at 17:10
  • @Lambie, one achieves such slowing down of an engine by restricting the supply of fuel. – PaulTanenbaum Dec 19 '23 at 17:12
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    "Full throttle" is also not really addressed in this answer, nor is the contradiction the OP requests clarification on. – Hank Dec 19 '23 at 17:13
  • @Hank, your comments have been addressed. – PaulTanenbaum Dec 19 '23 at 17:40
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    The two paragraphs of the current version of the answer do not explain the apparent contradiction; considered together, they exhibit it. If, as the first paragraph tells us, to throttle means to reduce the diameter of the opening, then one will expect full throttle to be a reduction of that diameter that goes as far as possible, that is to either zero or something close to zero. But the second paragraph tells us that it means the opposite: getting the diameter to be as large as possible. That is what the OP finds puzzling, and is hoping to get an explanation of. – jsw29 Dec 19 '23 at 23:51
  • “Throttle” meaning “strangle” isn't much of a surprise, since “throat” is right there. – Mark Dominus Dec 20 '23 at 17:19
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A throttle is a device that determines how much power a system produces. Full throttle means the system is producing as much power as possible.

The (probably) oldest version of this is a steam-ship or steam locomotive, where the boiler constantly produces steam and the throttle controls how much steam is allowed to enter the pistons or turbines that convert the steam power into motion. "Full throttle" in this case means the throttle is set wide-open, allowing as much steam as possible to enter the propulsion system. (On many ships, full throttle actually isn't as far open as the system can go; in this case they have a setting for "Flank" speed, which is actually as wide as the throttle can go, but can only be used for a short time without damaging the engines due to the stress involved. In this case 'flank' refers to the military maneuver of flanking: to attack from the sides or back of an opposing force to strike at their weakest points.)

Internal combustion engines, jets, and rockets have a similar situation, but in that case the throttle controls how much fuel enters the combustion chamber. At "full throttle", the system is introducing as much fuel as possible, producing the maximum possible energy output. On a car, the accelerator/gas pedal is the throttle (more or less -- in today's computer-mediated control systems, they're not exactly identical), but on an airplane it's a lever that's pushed forward to increase power or pulled back to reduce the power.

In internet terms, we sometimes talk about "getting throttled", which means the throughput is being reduced from its normal state. That's a metaphor to the physical device, with the implication that you're normally at full throttle, transmitting information as fast as possible, but server between the two endpoints may decide to intentionally limit your communication to more evenly distribute capacity among all the users (or to artificially slow down your connection for more nefarious reasons).

This use of the term 'throttle' is older than the internet; 'throttle' is a synonym for 'choke', as in "He grabbed the man by the neck and throttled him", which draws a metaphor between hands closing off the victim's airway and the throttle on an engine cutting off the flow of steam (or fuel) to the engine.

Darth Pseudonym
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