pond scum

American  

noun

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

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pond scum British  

noun

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

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Etymology

Origin of pond scum

First recorded in 1885–90

Example Sentences

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

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

From BBC ● Jul. 12, 2018

We still haven’t discovered intelligence or even believable evidence of pond scum anywhere else in the universe — not for lack of effort.

From New York Times ● May 10, 2018

The stench of fish and pond scum clung to him.

From "Made You Up" by Francesca Zappia