adjective.Impossible to achieve or overcome or be negotiated.
adjective.Overwhelming or insurmountable.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adjective.
incapable of being surmounted or excelled
adjective.
impossible to surmount
Word Usage
"He recalled the insuperable aversion the old man had ever entertained to approach of even make mention of the spot, and greatly did he blame himself for having persisted in offering a violence to his nature, the extent of which had been made so fearfully obvious."