unsurmountable
1. [ adjective ] not capable of being surmounted or overcome
Synonyms: insurmountable
Examples:

"insurmountable disadvantages"

Related terms: surmountable insuperable impossible unconquerable
2. [ adjective ] impossible to surmount or climb
Synonyms: unclimbable
Related terms: impassable
Similar spelling:   unmeasurable
  ungarmented
  unsurpassable
  unascribable