baseball player vs jock

baseball player and jock both are nouns.

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

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

Other hypernyms of baseball player include athlete, participant, player.

baseball player (noun)	jock (noun)
an athlete who plays baseball	a support for the genitals worn by men engaging in strenuous exercise
	a person trained to compete in sports