insoluble
in-sol-u-ble
adjective
A problem or difficulty that cannot be solved or dealt with.
"The economic crisis seemed insoluble."
adjective
Unable to dissolve in a liquid, forming a solid or suspension.
"Chalk is insoluble in water."
Thesaurus
Synonyms: unsolvable, unresolvable, insolvable, unsoluble, non-water-soluble, indissoluble, water-insoluble, hopeless
Antonyms: soluble