jellyfish
Americannoun
plural
jellyfish,plural
jellyfishes-
any of various marine coelenterates of a soft, gelatinous structure, especially one with an umbrellalike body and long, trailing tentacles; medusa.
-
Informal. a person without strong resolve or stamina; an indecisive or weak person.
noun
-
any marine medusoid coelenterate of the class Scyphozoa, having a gelatinous umbrella-shaped body with trailing tentacles
-
any other medusoid coelenterate
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informal a weak indecisive person
Etymology
Origin of jellyfish
1700–10; 1910–15 jellyfish for def. 2; jelly + fish
Explanation
A jellyfish is a marine animal with long tentacles that hang down from a bell-shaped body. Many jellyfish are nearly transparent. Jellyfish may look like they're made of jelly, but their bodies are actually 95 percent water. These umbrella-shaped creatures look graceful floating in the water, but they collapse into a flat blob on land. Jellyfish don't have organs, just a simple nervous system and three layers including the elastic, jelly-like mesoglea that gives them their name. In the 19th century, it became fairly common to call a weak person a jellyfish, a figurative usage that's still around today.
Vocabulary lists containing jellyfish
Reef Awareness Day, List 1
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Marine Biology - Introductory
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Marine Biology - Middle School
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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.
One is a tiny animal related to jellyfish that creates the hard reef structure.
From Science Daily • Feb. 12, 2026
Among the species discovered were ancient relatives of worms, sponges and jellyfish.
From Barron's • Jan. 28, 2026
The 28-year-old revealed her outfit was originally inspired by a jellyfish, which she saw in a book while reading to her two-year-old daughter.
From BBC • Jan. 20, 2026
I spent several hours spellbound by the aquarium—don’t miss the octopus and jellyfish tanks—and the museum of the world’s oceans.
From The Wall Street Journal • Jan. 10, 2026
Now and then a great jellyfish floated by, like an open umbrella made of glass, pulsing its way along just beneath the surface.
From "The Long-Lost Home" by Maryrose Wood
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.
