effluent

noun

: something that flows out: such as

a

: an outflowing branch of a main stream or lake

b

: waste material (such as smoke, liquid industrial refuse, or sewage) discharged into the environment especially when serving as a pollutant

Did you know?

Effluent comes from the Latin verb effluere, "to flow out". In an older meaning, an effluent was a stream flowing out of a river or lake. But nowadays effluent almost always means wastes that pour into our water and air. Liquid factory waste, smoke, and raw sewage can all be called effluents. An effluent filter keeps treated waste flowing out of a septic tank from clogging up its drainage pipes.

Examples of effluent in a Sentence

The factory has been accused of discharging effluent into the river.

Recent Examples on the Web

This water enters a stage known as secondary effluent. —Emma Hall, Sacbee.com, 3 June 2026

India’s environment court, the National Green Tribunal, has previously flagged regulatory gaps in the textile sector, noting that some units continue to discharge untreated effluent despite existing rules. —Ayushi Shah, CNN Money, 9 May 2026

When the effluent isn’t treated or is improperly stored, the chemicals can seep into groundwater and waterways, contaminating aquifers and rivers. —Abraham Nunbogu, Fortune, 29 Apr. 2026

As such, a portion of the intake water by-passes the aquariums and combines with the final effluent. —Staff Report, Hartford Courant, 25 Apr. 2026

Word History

First Known Use

1859, in the meaning defined above

Kids Definition

effluent

noun

ef·​flu·​ent

ˈef-ˌlü-ənt;

e-ˈflü-, 

ə-

: liquid (as sewage or industrial by-products) discharged as waste

effluent adjective