Definition of barrel sponge
: any of various large, usually cylindrical sponges (genus Xestospongia of the class Demospongiae) found especially on tropical coral reefs
I pass over the largest, healthiest barrel sponge I've ever seen—it seems plausible that I could fit inside it …— Scott Edler, Washington Post, 21 Oct. 2012
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Merriam-Webster unabridged
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Time Traveler for barrel sponge
The first known use of barrel sponge was in 1979
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