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

Two kiwis contain about 6 g of fiber, including both soluble and insoluble fiber. —Jennifer Berger, Verywell Health, 22 June 2026

The insoluble character of Alfa’s best records is reflected in his biography, which is difficult to neatly summarize. —H.d. Angel, Pitchfork, 16 June 2026

Bananas have soluble and insoluble fiber, both important types, Valente shares. —Alexandra Frost, USA Today, 12 June 2026

Most whole foods, like fruits, vegetables, and whole grains, contain a combination of insoluble and soluble fibers, but some are more concentrated in one than the other. —Jillian Kubala, Health, 29 May 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