pond scum

American

noun

any free-floating freshwater alga that forms a green scum on water.

pond scum British

noun

a greenish layer floating on the surface of stagnant waters, consisting of various freshwater algae

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of pond scum

First recorded in 1885–90

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

pond scum

But not long after the job was complete, the paint began to visibly peel, and the gleaming waters promptly refilled with green pond scum.

From Barron's ● Jun. 21, 2026

B. maeuseri presumably got its dinner in a very similar way, but also more flamingo-like, rippling tentatively through the shallows, slurping up mouthfuls of lagoon water and filtering out the pond scum.

From Salon ● Feb. 4, 2023

At those Olympics, everyone knew about the four-man crash and the pond scum.

From Washington Post ● Feb. 14, 2022

Trust me, if you soaked in a pond scum daily, you'd be as clean and green as me.

From BBC ● Jul. 12, 2018

Just thinking about it made me feel like pond scum again.

From "Out of My Mind" by Sharon M. Draper

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023