fireman vs twirler

fireman and twirler both are nouns.

Word	Noun	Adjective	Verb	Adverb
fireman	Yes	No	No	No
twirler	Yes	No	No	No

As nouns, twirler is a hypernym of fireman; that is, twirler is a word with a broader meaning than fireman:

Other hypernyms of fireman include hurler, pitcher.

fireman (noun)	twirler (noun)
play in which children pretend to put out a fire	(baseball) the person who does the pitching
a member of a fire department who tries to extinguish fires	someone who twirls a baton
a laborer who tends fires (as on a coal-fired train or steamship)
a pitcher who does not start the game