tennis player vs jock

tennis player and jock both are nouns.

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

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

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

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