9 letters · 11 points in Scrabble
adjective (of a substance) incapable of being dissolved
adjective admitting of no solution or explanation
adjective without hope of solution
originFrom Middle English insolible, from Middle French insoluble, from Latin insolūbilis, from in- + solūbilis. Piecewise doublet of insolvable and unsolvable. By surface analysis, in- + soluble.
Etymology from Wiktionary, CC BY-SA 3.0