drop-dead vs vernacular

drop-dead is not a noun while vernacular is a noun.

Word	Noun	Adjective	Verb	Adverb
drop-dead	No	No	No	Yes
vernacular	Yes	Yes	No	No

drop-dead (noun)	vernacular (noun)
	the everyday speech of the people (as distinguished from literary language)
	a characteristic language of a particular group (as among thieves)

drop-dead (adjective)	vernacular (adjective)
	being or characteristic of or appropriate to everyday language

drop-dead (adverb)	vernacular (adverb)
stunningly or breathtakingly