Word (or phrase) that means something you thought was a great idea, that turns out to be a massive error

Question

We have a variety of suggestions for something that you thought was bad, but turned out to be good.

Is there a single word that describes something that you thought was going to be a brilliant idea that turns out to be an apocalyptic blunder.

"His idea was an x"

It Seemed Like a Good Idea at the Time gets its own dedicated entry on TVTropes (but don't follow that link unless you've got an afternoon to spare! :) Pragmatically, whenever you hear that phrase, you know it refers to something which in hindsight was in fact the height of stupidity. — FumbleFingers, Jun 15 '16 at 16:26
Related: http://english.stackexchange.com/questions/100452/word-or-phrase-for-a-much-hyped-discovery-which-later-turns-out-to-be-insignifi — Kevin Workman, Jun 15 '16 at 18:11
If there isn't yet a word for this, boy do we (humankind) need one! And when I find it I will certainly popularize it vigorously. — MickeyfAgain_BeforeExitOfSO, Jun 15 '16 at 20:00
You might need to settle for a metaphorical reference. His idea was an Iraq Invasion. — jxh, Jun 15 '16 at 20:29
How about "the road to Hell is paved with good intentions.". Not sure if that's too"harsh" — BruceWayne, Jun 16 '16 at 05:17

score 2 · Answer 1 · answered Jun 16 '16 at 04:24

2

See goldbrick

odo

A thing that looks valuable, but is in fact worthless.

answered Jun 16 '16 at 04:24

vickyace

14,859

score 2 · Answer 2 · answered Jun 21 '16 at 03:09

2

The first comment on the question you link to suggests “a blessing in disguise,” which made me think of a wolf in sheep’s clothing, which refers to someone (or something) that initially appears benign, but is ultimately revealed to be harmful.

I’m not sure how well this fits your use case, but bait and switch seems to be related:

a selling method in which a customer is attracted by the advertisement of a low-priced product but then is encouraged to buy a more expensive one

i.e., something appears to be a bargain (a good deal), but you end up getting a worse deal than you expected.

answered Jun 21 '16 at 03:09

Scott - Слава Україні

7,276

Hmm. Perhaps "A pig in a poke"? – Richard Jun 21 '16 at 06:18
I think of "a pig in a poke" as referring to (getting) something of unknown quality. It doesn't necessarily imply that you've been promised something that is good, or that it turns out to be bad (although the clear implication is that you risk such an outcome). If you prefer the uncertainty angle, you could use "His idea was a *roll of the dice", "... a shot in the dark," or perhaps "... a leap of faith*." – Scott - Слава Україні Jun 22 '16 at 02:14

k1eran · Answer 3 · 2016-06-15T19:40:47.050

0

His approach turned out to be a dead end.

a situation, plan, or way of doing something that leads to nothing further — M-W

Plus synonyms like blind alley, cul-de-sac, false-positive.

EDIT Also at http://www.thefreedictionary.com/erroneousness some more options like :

off base - Badly mistaken, completely wrong.
Barking up the wrong tree - To pursue a false lead.
And lots more.

edited Jun 15 '16 at 19:40

answered Jun 15 '16 at 19:17

k1eran

22,565

I'm not feeling it. "Dead end" doesn't really imply catastrophic failure, just failure. – Richard Jun 15 '16 at 19:33
Nor does it imply that the original idea was brilliant. A dead end can just as easily result from a mediocre idea. – vynsane Jun 15 '16 at 20:45

Word (or phrase) that means something you thought was a great idea, that turns out to be a massive error

3 Answers3