in ‧ sol ‧ va ‧ ble /ɪnˈsɒlvəb ə l $ ɪnˈsɑːl-/ BrE AmE adjective especially American English
[ Word Family: noun : ↑ solution , ↑ solvent , ↑ solubility , ↑ insolvency ; adjective : ↑ soluble ≠ ↑ insoluble , ↑ unsolved , ↑ solvent ≠ ↑ insolvent , ↑ solvable ≠ ↑ insolvable ; verb : ↑ solve ; adverb : ↑ insolvably ]
an insolvable problem is or seems impossible to solve SYN insoluble
—insolvably adverb