comic vs gagman

comic and gagman both are nouns.

Word	Noun	Adjective	Verb	Adverb
comic	Yes	Yes	No	No
gagman	Yes	No	No	No

As nouns, gagman is a hyponym of comic; that is, gagman is a word with a more specific, narrower meaning than comic:

comic (noun)	gagman (noun)
a professional performer who tells jokes and performs comical acts	someone who writes comic material for public performers
	a comedian who uses gags

comic (adjective)	gagman (adjective)
of or relating to or characteristic of comedy
arousing or provoking laughter