gig-mill vs gig mill

gig-mill and gig mill both are nouns.

Word	Noun	Adjective	Verb	Adverb
gig-mill	Yes	No	No	No
gig mill	Yes	No	No	No

As nouns, gig-mill and gig mill are synonyms defined as:

gig-mill and gig mill: a textile mill employing rotary wire cylinders for napping.

gig-mill (noun)	gig mill (noun)
a textile mill employing rotary wire cylinders for napping.	a textile mill employing rotary wire cylinders for napping.