insurmountable vs unsurmountable

insurmountable and unsurmountable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
insurmountable	No	Yes	No	No
unsurmountable	No	Yes	No	No

As adjectives, insurmountable and unsurmountable are synonyms defined as:

insurmountable and unsurmountable: not capable of being surmounted or overcome

insurmountable (adjective)	unsurmountable (adjective)
not capable of being surmounted or overcome	not capable of being surmounted or overcome
impossible to surmount	incapable of being surmounted or climbed