two-baser vs two-base hit

two-baser and two-base hit both are nouns.

Word	Noun	Adjective	Verb	Adverb
two-baser	Yes	No	No	No
two-base hit	Yes	No	No	No

As nouns, two-baser and two-base hit are synonyms defined as:

two-baser and two-base hit: a base hit on which the batter stops safely at second base

Other synonyms of two-baser include double, two-bagger.

two-baser (noun)	two-base hit (noun)
a base hit on which the batter stops safely at second base	a base hit on which the batter stops safely at second base