pond scum

noun

1
: any of various algae (especially spirogyra) or cyanobacteria
2
: a mass of tangled filaments of algae or cyanobacteria in stagnant waters

Examples of pond scum in a Sentence

Recent Examples on the Web
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Minnesota This machine, which is hitched to a trailer and taken to a wastewater treatment facility in Rosemount, converts pond scum into biodiesel, at the Biosystems and Agricultural Engineering Building in St. Paul, Minnesota. Scott Cohn, CNBC, 22 July 2025 Algae: The Food of the Future of the Past In the years following World War II, American and European food scientists hoped to feed the world with common pond scum supplemented with plastics. JSTOR Daily, 24 June 2024 Yet the evidence for cogitating pond scum grows daily. Rowan Jacobsen, Scientific American, 1 Feb. 2024 After a lovely day of rolling in the grass, digging in the dirt, playing in mud or pond scum, bathe your pet with Calm Shampoo, which is a one-of-a-kind day at the spa for Rocco & Roxie Supply Co.'s dogs. Amber Smith, Discover Magazine, 22 Oct. 2022

Word History

First Known Use

1864, in the meaning defined at sense 1

Time Traveler
The first known use of pond scum was in 1864

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Cite this Entry

“Pond scum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pond%20scum. Accessed 9 Sep. 2025.

Kids Definition

pond scum

noun
1
: spirogyra
also : any of various related algae
2
: a mass of tangled threads of algae in still water

More from Merriam-Webster on pond scum

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