thick-skulled vs thickheaded

thick-skulled and thickheaded both are adjectives.

Word	Noun	Adjective	Verb	Adverb
thick-skulled	No	Yes	No	No
thickheaded	No	Yes	No	No

As adjectives, thick-skulled and thickheaded are synonyms defined as:

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

thick-skulled (adjective)	thickheaded (adjective)
(used informally) stupid	(used informally) stupid