"insolvable" in the adjective sense
1. insolvable, unsoluble, unsolvable, unresolvable
not easily solved
"an apparantly insolvable problem"
"public finance...had long presented problems unsolvable or at least unsolved"- C.L.Jones
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License