bat boy vs male child

bat boy and male child both are nouns.

Word	Noun	Adjective	Verb	Adverb
bat boy	Yes	No	No	No
male child	Yes	No	No	No

As nouns, male child is a hypernym of bat boy; that is, male child is a word with a broader meaning than bat boy:

bat boy: (baseball) a boy who takes care of bats and other baseball equipment
male child: a youthful male person

Other hypernyms of bat boy include assistant, help, helper, supporter, boy.

bat boy (noun)	male child (noun)
(baseball) a boy who takes care of bats and other baseball equipment	a youthful male person