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

• 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

Chia seeds provide both soluble and insoluble fiber, plus protein, omega-3 fats, and minerals. —Morgan Pearson, Verywell Health, 22 Aug. 2025

Just one cup has over 11 grams of both soluble and insoluble fiber. —Ashia Aubourg, Outside, 16 Aug. 2025

There are two main types of fiber—soluble and insoluble—and each works differently in the gut. —Christina Manian, Health, 14 Aug. 2025

Resolution of this tragic dynamic appears insoluble. —David Marks, The Orlando Sentinel, 8 Aug. 2025

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