stop leak vs stop-leak

stop leak and stop-leak both are nouns.

Word	Noun	Adjective	Verb	Adverb
stop leak	Yes	No	No	No
stop-leak	Yes	No	No	No

As nouns, stop leak and stop-leak are synonyms defined as:

stop leak and stop-leak: a liquid that is added to the radiator to stop leaks.

stop leak (noun)	stop-leak (noun)
a liquid that is added to the radiator to stop leaks.	a liquid that is added to the radiator to stop leaks.