deaf as a post vs deaf

deaf as a post is not a noun while deaf is a noun.

Word	Noun	Adjective	Verb	Adverb
deaf as a post	No	Yes	No	No
deaf	Yes	Yes	Yes	No

deaf as a post (noun)	deaf (noun)
	people who have severe hearing impairments

deaf as a post (adjective)	deaf (adjective)
totally deaf; unable to hear anything	lacking or deprived of the sense of hearing wholly or in part
	(usually followed by `to') unwilling or refusing to pay heed

deaf as a post (verb)	deaf (verb)
	make or render deaf