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pond scum

American  

noun

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

pond scum British  

noun

  1. 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.

Pond scum might seem like a dubious way to honor someone.

From Slate • Jun. 14, 2022

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

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.