blowhole vs vent-hole

blowhole and vent-hole both are nouns.

Word	Noun	Adjective	Verb	Adverb
blowhole	Yes	No	No	No
vent-hole	Yes	No	No	No

As nouns, blowhole and vent-hole are synonyms defined as:

Other synonyms of blowhole include vent, venthole.

blowhole (noun)	vent-hole (noun)
a hole for the escape of gas or air	a hole for the escape of gas or air
the spiracle of a cetacean located far back on the skull