grounder vs ground ball

grounder and ground ball both are nouns.

Word	Noun	Adjective	Verb	Adverb
grounder	Yes	No	No	No
ground ball	Yes	No	No	No

As nouns, grounder and ground ball are synonyms defined as:

grounder and ground ball: (baseball) a hit that travels along the ground

Other synonyms of grounder include groundball, hopper.

grounder (noun)	ground ball (noun)
(baseball) a hit that travels along the ground	(baseball) a hit that travels along the ground