fighter vs skirmisher

fighter and skirmisher both are nouns.

Word	Noun	Adjective	Verb	Adverb
fighter	Yes	No	No	No
skirmisher	Yes	No	No	No

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

fighter (noun)	skirmisher (noun)
a high-speed military or naval airplane designed to destroy enemy aircraft in the air	someone who skirmishes (e.g., as a member of a scouting party)
someone who fights (or is fighting)
someone who fights for a cause