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

• hopeless
• impossible
• insolvable
• insuperable
• unattainable
• undoable
• unrealizable
• unsolvable

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

Soluble and insoluble fibers help promote regular bowel movements. —Larell Scardelli, Verywell Health, 5 Mar. 2025

The bottom line: Juicing fruits and vegetables removes most insoluble fiber from the foods, and fiber is key. —Maya Goldman, Axios, 10 Feb. 2025

That's because fiber-rich foods naturally tend to have a mix of multiple fibers, which can be categorized into two types: soluble and insoluble. —Erica Sloan, SELF, 19 Feb. 2025

Each pulse or lentil has different ratios of soluble and insoluble fibers. —Merve Ceylan, Health, 11 Feb. 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