This is a bit hard to explain, so let's try an example.
There is something called "rock art", which means human-made markings placed on natural stone.
Those two words when put together have a specific meaning. The name on the other hand may imply that any art made of rocks could be called rock art.
Is there any way to describe this type of name/phrase?
THE DUPLICATE YOU PICKED IS NOT THE SAME QUESTION. This isn't about an adjective. It's about a group of words that have a specific meaning that are more than the sum of their parts.