UNSURMOUNTABLE

unsurmountable, unclimbable

(adjective) incapable of being surmounted or climbed

insurmountable, unsurmountable

(adjective) not capable of being surmounted or overcome; “insurmountable disadvantages”

Source: WordNet® 3.1

Etymology

Adjective

unsurmountable (comparative more unsurmountable, superlative most unsurmountable)

insurmountable

Source: Wiktionary

Un`sur*mount"a*ble, a.

Definition: Insurmountable. Locke.

Source: Webster’s Unabridged Dictionary 1913 Edition