thickheaded vs fatheaded

thickheaded and fatheaded both are adjectives.

Word	Noun	Adjective	Verb	Adverb
thickheaded	No	Yes	No	No
fatheaded	No	Yes	No	No

As adjectives, thickheaded and fatheaded are synonyms defined as:

Other synonyms of thickheaded include blockheaded, boneheaded, duncical, duncish, loggerheaded, thick-skulled, thick, wooden-headed.

thickheaded (adjective)	fatheaded (adjective)
(used informally) stupid	(used informally) stupid