twirler vs thrower

twirler and thrower both are nouns.

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

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

twirler: (baseball) the person who does the pitching
thrower: someone who projects something (especially by a rapid motion of the arm)

Other hypernyms of twirler include ballplayer, baseball player.

twirler (noun)	thrower (noun)
(baseball) the person who does the pitching	someone who projects something (especially by a rapid motion of the arm)
someone who twirls a baton	a craftsman who shapes pottery on a potter's wheel and bakes them in a kiln
	a person who twists silk or rayon filaments into a thread or yarn