break dance vs break-dance

break dance is a noun but break-dance is not a noun.

Word	Noun	Adjective	Verb	Adverb
break dance	Yes	No	Yes	No
break-dance	No	No	Yes	No

As verbs, break dance and break-dance are synonyms defined as:

Other synonyms of break dance include break.

break dance (noun)	break-dance (noun)
a form of solo dancing that involves rapid acrobatic moves in which different parts of the body touch the ground; normally performed to the rhythm of rap music

break dance (verb)	break-dance (verb)
do a break dance	do a break dance