venthole vs blowhole

venthole and blowhole both are nouns.

Word	Noun	Adjective	Verb	Adverb
venthole	Yes	No	No	No
blowhole	Yes	No	No	No

As nouns, venthole and blowhole are synonyms defined as:

Other synonyms of venthole include vent-hole, vent.

venthole (noun)	blowhole (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