fathead vs jackass

fathead and jackass both are nouns.

Word	Noun	Adjective	Verb	Adverb
fathead	Yes	No	No	No
jackass	Yes	No	No	No

As nouns, fathead and jackass are synonyms defined as:

Other synonyms of fathead include bozo, cuckoo, goof, goofball, goose, twat, zany.

fathead (noun)	jackass (noun)
a man who is a stupid incompetent fool	male donkey
	a man who is a stupid incompetent fool