The room was crawling with vermin.

I think the room can't crawl by itself.

So is the sentence idiomatic or grammatical?


2 Answers 2


Yes, this is an idiom. "be crawling with something" See https://dictionary.cambridge.org/dictionary/english/crawling-with

As an idiom it means that the literal or logical meaning of "crawl" isn't being used. Rooms can't crawl, but that is irrelevant to the idiomatic meaning.

It is grammatical, and would be even if the idiom didn't exist. Grammar has very little to do with whether something is true or possible or logical. This is why "Colourless green ideas sleep furiously" is grammatically good, but utterly meaningless.


There is a joke, an old chestnut, which asks

“Why is it that our nose runs, but our feet smell?”
Ans: “Because we are built upside down.”

Obviously, noses are physically incapable of running, but the meaning refers to an excessive production of mucus that builds up in our nose and flows (runs) out of the nasal cavity. Feet that smell refers to odour which emanates, often highly unpleasant, from human feet.

Similarly, the expression a room crawling with bugs, does not mean a room is able to crawl but that it is covered with crawling bugs.

These are all metaphors, expressions that often refer to commonplace situations, they are not meant to be interpreted literally.

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