openmouthed vs colloquialism

openmouthed is not a noun while colloquialism is a noun.

Word	Noun	Adjective	Verb	Adverb
openmouthed	No	Yes	No	No
colloquialism	Yes	No	No	No

openmouthed (noun)	colloquialism (noun)
	a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech

openmouthed (adjective)	colloquialism (adjective)
with eyes or mouth open in surprise