unaccustomed vs unusual

unaccustomed and unusual both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unaccustomed	No	Yes	No	No
unusual	No	Yes	No	No

unaccustomed (adjective)	unusual (adjective)
unusual or unfamiliar	not usual or common or ordinary
	being definitely out of the ordinary and unexpected; slightly odd or even a bit weird
	not commonly encountered