• WordNet 3.6
    • adj unsurmountable incapable of being surmounted or climbed
    • adj unsurmountable not capable of being surmounted or overcome "insurmountable disadvantages"
    • ***
Webster's Revised Unabridged Dictionary
    • a Unsurmountable Insurmountable.
    • ***
Chambers's Twentieth Century Dictionary
    • adj Unsurmountable un-sur-mown′ta-bl insurmountable.
    • ***


In literature:

He also considers the difficulties of a journey to Germany under the present conditions to be almost unsurmountable.
"The Coming Conquest of England" by August Niemann
A great, unsurmountable wall seemed to obstruct Ellen's thought.
"To the Last Man" by Zane Grey
One difficulty confronted him, and until he had mentioned it to Hogan seemed unsurmountable he had need of a ship.
"The Tavern Knight" by Rafael Sabatini
The ignorant man sees only the unsurmountable wall of death, hiding, seemingly forever, his cherished friends.
"Autobiography of a YOGI" by Paramhansa Yogananda
This war is gradually crumbling the once unsurmountable wall of caste.
"Over The Top" by Arthur Guy Empey
But what ground was now unsurmountable to Roman valour?
"The History of Rome; Books Nine to Twenty-Six" by Titus Livius
He had not been at Frankfort a year before he had learnt to look on this hostility of Austria as unsurmountable.
"Bismarck and the Foundation of the German Empire" by James Wycliffe Headlam
Then they reached a large stream with an almost unsurmountable mountain to the west.
"A Backward Glance at Eighty" by Charles A. Murdock
That's an unsurmountable objection at the start.
"Big Game" by Mrs. George de Horne Vaizey
In water-leg boilers, the use of such flat-stayed surfaces under pressure presents difficulties that are practically unsurmountable.
"Steam, Its Generation and Use" by Babcock & Wilcox Co.

In science:

The difficult for users to share long streams of secret keys beforehand has been an unsurmountable barrier preventing widespread use of one-time pad systems.
Secure sharing of random bits over the Internet
With enough work, in the near future we should be able to establish that either the diverse goals of the program can in fact be met or that the program encounters specific unsurmountable obstacles.
Overview and Outlook
However, it has not run into an unsurmountable obstacle either.
Overview and Outlook
The unsurmountable problems encountered in an ensemble interpretation of the wave function (or of any other superposition, such as |ai + |bi) are reflected by the fact that there is no ensemble entropy that would represent the unknown property-to-be-measured (see the first step of Fig. 2.2 or 2.3 – cf. also Zurek 1984).
Decoherence: Basic Concepts and Their Interpretation
At the moment we failed to derive the analogous expression for almost-symmetric (slightly asymmetric) real random matrices due to unsurmountable technical problems.
Almost-Hermitian Random Matrices: Eigenvalue Density in the Complex Plane