twirler vs reliever

twirler and reliever both are nouns.

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

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

twirler (noun)	reliever (noun)
(baseball) the person who does the pitching	a pitcher who does not start the game
someone who twirls a baton	someone who takes the place of another (as when things get dangerous or difficult)
	a person who reduces the intensity (e.g., of fears) and calms and pacifies