colloquialism vs openmouthed

colloquialism is a noun but openmouthed is not a noun.

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

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

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