ballcock vs ball cock

ballcock and ball cock both are nouns.

Word	Noun	Adjective	Verb	Adverb
ballcock	Yes	No	No	No
ball cock	Yes	No	No	No

As nouns, ballcock and ball cock are synonyms defined as:

ballcock and ball cock: floating ball that controls level in a water tank

ballcock (noun)	ball cock (noun)
floating ball that controls level in a water tank	floating ball that controls level in a water tank