Synonyms of insoluble

insoluble

adjective

(ˌ)in-ˈsäl-yə-bəl 

as in impossible

incapable of being solved or accomplished

the seemingly insoluble mystery concerning the identity of the people who built these ancient structures

Synonyms & Similar Words

• impossible
• hopeless
• unlikely
• problematic
• insolvable
• unsolvable
• insuperable
• futile
• unattainable
• impractical
• unrealizable
• undoable
• useless
• incredible
• absurd
• unworkable
• impracticable
• unusable
• questionable
• infeasible
• dubious
• improbable
• suspect
• inconceivable
• debatable
• unfeasible
• disputable
• suspicious
• implausible
• fishy
• unthinkable
• shaky
• unimaginable
• unbelievable
• doubtful
• ridiculous
• far-fetched
• doubtable
• outlandish
• shady
• preposterous
• fantastic

Antonyms & Near Antonyms

• soluble
• possible
• feasible
• workable
• practical
• achievable
• attainable
• useful
• applicable
• functional
• reasonable
• usable
• resolvable
• practicable
• working
• realizable
• probable
• serviceable
• likely
• doable
• acceptable
• plausible
• conceivable
• credible
• believable

Example Sentences

Recent Examples of insoluble

Both minerals bind together in the digestive tract to form insoluble calcium oxalate, which naturally prevents the body from absorbing essential calcium. — Ayesha Gulzar, Verywell Health, 18 Aug. 2026

Fiber, including both soluble and insoluble fiber, play critical roles in gut health. — Jillian Kubala, HEALTH, 4 Aug. 2026

The seeds hold most of the insoluble fiber, and the skin adds even more, according to Martorano. — Olivia McIntosh, Martha Stewart, 22 July 2026

Many popular houseplants contain insoluble calcium oxalate crystals, tiny needle-like structures found in their leaves and stems. — Ryan Brennan, Fort Worth Star-Telegram, 14 July 2026