unclimbable a incapable of being ascended s incapable of being surmounted or climbed Usage(s) For years, K-2 has been regarded as unclimbable. Two days later, the rescue attempt was called off due to bad weather and the difficulties involved in climbing an almost unclimbable mountain in the hopes of finding Prez alive. An "unclimbable" fence will be erected to in-close a compound. Synonym(s) unscalable unsurmountable Antonym(s) scalable