deaf as a post vs stone-deaf

deaf as a post and stone-deaf both are adjectives.

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

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

Other synonyms of deaf as a post include profoundly deaf, unhearing.

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