unsurmountable vs insurmountable

unsurmountable and insurmountable both are adjectives.

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

As adjectives, unsurmountable and insurmountable are synonyms defined as:

unsurmountable and insurmountable: not capable of being surmounted or overcome

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