imprison vs gaol

imprison is not a noun while gaol is a noun.

Word	Noun	Adjective	Verb	Adverb
imprison	No	No	Yes	No
gaol	Yes	No	Yes	No

As verbs, imprison and gaol are synonyms defined as:

Other synonyms of imprison include immure, incarcerate, jail, jug, lag, put away, put behind bars, remand.

imprison (noun)	gaol (noun)
	a correctional institution used to detain persons who are in the lawful custody of the government (either accused persons awaiting trial or convicted persons serving a sentence)

imprison (verb)	gaol (verb)
lock up or confine, in or as in a jail	lock up or confine, in or as in a jail
confine as if in a prison