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

The main ingredient — chickpeas — is a nutritional powerhouse that provides protein along with both soluble and insoluble fibers, making a serving (or two) excellent for gut health. —Gretchen McKay, Twin Cities, 15 Jan. 2026

Dietitians say the fruit's sweet pulp and tiny seeds provide both soluble and insoluble fiber, helping improve regularity while also supplying antioxidants and key minerals that support overall health. —Deirdre Bardolf, FOXNews.com, 3 Jan. 2026

There are two main types of fiber: soluble and insoluble. —Daryl Austin, USA Today, 1 Dec. 2025

There are two main types of dietary fiber—soluble and insoluble—and many foods contain a combo of the two. —Danielle Zickl, SELF, 27 Nov. 2025