relief pitcher vs twirler

relief pitcher and twirler both are nouns.

Word	Noun	Adjective	Verb	Adverb
relief pitcher	Yes	No	No	No
twirler	Yes	No	No	No

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

Other hypernyms of relief pitcher include hurler, pitcher.

relief pitcher (noun)	twirler (noun)
a pitcher who does not start the game	(baseball) the person who does the pitching
	someone who twirls a baton