1) Insoluble 2) Not easily solved 3) Unresolvable 4) Unsoluble 5) Unsolvable 1) Unresolvable 2) Unsoluble 3) Unsolvable 
• (a.) Not solvable; insoluble; admitting no solution or explanation; as, an insolvable problem or difficulty. • (a.) Not capable of being loosed or disentangled; inextricable. • (a.) Incapable of being paid or discharged, as debts.
In·solv'a·ble adjective 1. Not solvable; insoluble; admitting no solution or explanation; as, an insolvable problem or difficulty. I. Watts. 2. Incapable of being paid or discharged, as debts. 3. Not capable of being loosed or disentangled; inextricable. 'Band...
[adj] - not easily solved
unsoluble adjective not easily solved; `an apparantly insolvable problem`; `public finance...had long presented problems unsolvable or at least unsolved`- C.L.Jones
incapable of being solved or explained; insoluble.