feign vs mouth

feign is not a noun while mouth is a noun.

Word	Noun	Adjective	Verb	Adverb
feign	No	No	Yes	No
mouth	Yes	No	Yes	No

As verbs, mouth is a hyponym of feign; that is, mouth is a word with a more specific, narrower meaning than feign:

Other hyponyms of feign include play possum, take a dive, bull, bullshit, fake, talk through one's hat.

feign (noun)	mouth (noun)
	the opening of a jar or bottle
	the externally visible part of the oral cavity on the face and the system of organs surrounding the opening
	the opening through which food is taken in and vocalizations emerge
	an impudent or insolent rejoinder
	the point where a stream issues into a larger body of water
	an opening that resembles a mouth (as of a cave or a gorge)
	a person conceived as a consumer of food
	a spokesperson (as a lawyer)

feign (verb)	mouth (verb)
make believe with the intent to deceive	express in speech
make a pretence of	articulate silently; form words with the lips only
	touch with the mouth