hitter vs baseball player

hitter and baseball player both are nouns.

Word	Noun	Adjective	Verb	Adverb
hitter	Yes	No	No	No
baseball player	Yes	No	No	No

As nouns, baseball player is a hypernym of hitter; that is, baseball player is a word with a broader meaning than hitter:

Other hypernyms of hitter include ballplayer.

hitter (noun)	baseball player (noun)
(baseball) a ballplayer who is batting	an athlete who plays baseball
someone who hits