insoluble
adjective
1. (of a substance) incapable of being dissolved
Similar word(s): indissoluble
2. admitting of no solution or explanation
- an insoluble doubt
Similar word(s): incomprehensible, inexplicable, insolvable, unresolvable, unsoluble, unsolvable
3. without hope of solution
- an insoluble problem
Similar word(s): hopeless