in the lurch vs idiomatic expression

in the lurch is not a noun while idiomatic expression is a noun.

Word	Noun	Adjective	Verb	Adverb
in the lurch	No	No	No	Yes
idiomatic expression	Yes	No	No	No

in the lurch (noun)	idiomatic expression (noun)
	an expression whose meanings cannot be inferred from the meanings of the words that make it up

in the lurch (adverb)	idiomatic expression (adverb)
in a difficult or vulnerable position