thrower vs hurler

thrower and hurler both are nouns.

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

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

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

Other hyponyms of thrower include pelter, pitcher, twirler, slinger, tosser.

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