Impossible to surmount; insuperable: insurmountable difficulties. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "insurmountable" in a sentence
"Dean Knowles, the most senior dean in the country, said the cathedral clergy had been put "under a great deal of strain" as they faced what he described as "insurmountable issues" and that his position had become "untenable"."
"What would be the point of the remaining contests if Obama's lead after Tuesday in insurmountable?"
"We were inclosed by a natural wall, rising steep on every side to a height which produced the idea of insurmountable confinement."