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

Greek Yogurt With Flaxseed and Prunes Yogurt with live cultures may help support gut bacteria, while ground flaxseed provides both soluble and insoluble fiber. — Sarah Jividen, Verywell Health, 23 July 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