D defs.my
Entry 3 senses Webster, 1913

Insoluble

/ĭnˌ-säl'-yəb-əl/ · In·sol·u·ble · IPA /ɪnˈsɑljəbəl/
01 a. Not soluble; in capable or difficult of being dissolved, as by a liquid; as, chalk is insoluble in water.
  1. 1.
    Not soluble; in capable or difficult of being dissolved, as by a liquid; as, chalk is insoluble in water.
  2. 2.
    Not to be solved or explained; insolvable; as, an insoluble doubt, question, or difficulty.
  3. 3.
    Strong.[Obs.]