insoluble

adjective

in·​sol·​u·​ble (ˌ)in-ˈsäl-yə-bəl 

: not soluble: such as

a

: incapable of being dissolved in a liquid and especially water

also : soluble only with difficulty or to a slight degree

b

: having or admitting of no solution or explanation

an insoluble problem

c

archaic : indissoluble

insolubility

(ˌ)in-ˌsäl-yə-ˈbi-lə-tē 

noun

insoluble noun

insolubleness

(ˌ)in-ˈsäl-yə-bəl-nəs 

noun

insolubly

(ˌ)in-ˈsäl-yə-blē 

adverb

Synonyms of insoluble

• impossible
• hopeless

Examples of insoluble in a Sentence

a substance insoluble in water

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

Recent Examples on the Web

Because insoluble fiber is not actually digested, it’s broken down and fermented by the good bacteria in your gut, which produce short-chain fatty acids that signal to your liver to stop producing as much glucose. — Mira Miller, Verywell Health, 17 Sep. 2026

Apples also contain multiple types of fiber, including soluble fiber (which promotes healthy cholesterol levels) and insoluble fiber (which benefits digestion), says Elick. — Kirsten Nunez, Martha Stewart, 31 Aug. 2026

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

Word History

Etymology

Middle English insolible, from Latin insolubilis, from in- + solvere to free, dissolve — more at solve

First Known Use

14th century, in the meaning defined above

Rhymes for insoluble

• soluble
• voluble
• indissoluble
• revoluble

Kids Definition

insoluble

adjective

in·​sol·​u·​ble (ˈ)in-ˈsäl-yə-bəl 

1

: impossible to solve

an insoluble problem

2

: impossible or difficult to dissolve

a substance insoluble in water

Medical Definition

insoluble

adjective

in·​sol·​u·​ble (ˈ)in-ˈsäl-yə-bəl 

: incapable of being dissolved in a liquid

also : soluble only with difficulty or to a slight degree