pond scum

noun

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

pond scum

noun

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

Word History and Origins

Origin of pond scum¹

First recorded in 1885–90

Example Sentences

So they placed the air sampler on the shore of a small pond during a bloom of pond scum.

From Science News For Students

His group knew the pond scum responsible could release toxins that might enter the air.

From Science News For Students