in the lurch vs idiom

in the lurch is not a noun while idiom is a noun.

Word	Noun	Adjective	Verb	Adverb
in the lurch	No	No	No	Yes
idiom	Yes	No	No	No

in the lurch (noun)	idiom (noun)
	the style of a particular artist or school or movement
	the usage or vocabulary that is characteristic of a specific group of people
	an expression whose meanings cannot be inferred from the meanings of the words that make it up
	a manner of speaking that is natural to native speakers of a language

in the lurch (adverb)	idiom (adverb)
in a difficult or vulnerable position