unimportant vs insignificant

unimportant and insignificant both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unimportant	No	Yes	No	No
insignificant	No	Yes	No	No

As adjectives, unimportant and insignificant are synonyms defined as:

unimportant (adjective)	insignificant (adjective)
not important	devoid of importance, meaning, or force
devoid of importance, meaning, or force	signifying nothing
	of little importance or influence or power; of minor status
	small and unimpressive