deaf as a post vs unhearing

deaf as a post and unhearing both are adjectives.

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

As adjectives, deaf as a post and unhearing are synonyms defined as:

Other synonyms of deaf as a post include profoundly deaf, stone-deaf.

deaf as a post (adjective)	unhearing (adjective)
totally deaf; unable to hear anything	totally deaf; unable to hear anything