The adjective stagnant means something that is not moving, running, or with just a little action or change.

Synonyms are motionless, idle, static, or listless.

The word origins from French (early 17th century) stagnant, from Latin stagnantem (nominative stagnans), present participle of stagnare meaning “to stagnate”.

Stagnant water is one of the major breeding grounds for mosquitoes.

The committee sought advice on how to revive the stagnant economy.

She lived a stagnant life before she met him.