jel·​ly·​fish | \ ˈje-lē-ˌfish How to pronounce jellyfish (audio) \

Definition of jellyfish

1a : the typically free-swimming, bell-shaped, usually sexually-reproducing solitary or colonial form of a cnidarian in which the whorls of tentacles lined with nematocysts arise and hang down from the margin of the nearly transparent, gelatinous bell : medusa especially : a large medusa characteristic of the siphonophores and scyphozoans (such as the sea nettle or box jellyfish)
2 : a person lacking backbone or firmness

Illustration of jellyfish

Illustration of jellyfish

jellyfish 1a

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Synonyms & Antonyms for jellyfish



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Examples of jellyfish in a Sentence

a jellyfish who was afraid to tell her boss that her latest brainstorm was just plain bad
Recent Examples on the Web Why are all these jellyfish in the fells point harbor? Penelope Blackwell,, "Jellyfish in Baltimore’s Inner Harbor? Here’s why people are seeing more of them.," 8 Oct. 2020 Watch jellyfish delicately swim in and out of the frame, or enjoy the aquarium’s largest exhibition, an awe-inspiring, one million-gallon tank that houses an array of sea creatures, including stingray, sharks and turtles. Sara Aridi, New York Times, "The Best Live Animal Feeds From Around the World," 3 Oct. 2020 Cnidarians—a group of animals that includes sea anemones, jellyfish and corals—are highly adaptable. Claire Bugos, Smithsonian Magazine, "These Sea Anemones Grow Limbs When They Eat," 15 Sep. 2020 On July 2, McDonald Observatory dark sky specialist Stephen Hummel photographed a red jellyfish sprite from Texas’ Mount Locke. Theresa Machemer, Smithsonian Magazine, "How to Spot Elusive ‘Jellyfish Sprites’ Dancing in the Sky During a Thunderstorm," 12 Aug. 2020 Her door swung open and the spill of light from the hallway washed over the ceiling and drowned her jellyfish. Susan Choi, The New Yorker, "Flashlight," 31 Aug. 2020 Kittens and puppies from the Atlanta Humane Society got in on the action last week, visiting jellyfish at the Georgia Aquarium, according to the Society’s statement. Nora Mcgreevy, Smithsonian Magazine, "Animals Are Taking Adorable Field Trips During Quarantine," 10 Apr. 2020 That was until my babysitter that year, my grandmother, regaled me with stories and pictures from encyclopedias of riptides, crashing waves, sharks, lampreys, and jellyfish. Susan Bro, Fortune, "My daughter Heather Heyer’s death taught me how to grieve. We all need to know how today," 12 Aug. 2020 Sounds like a Bay Area band, Shed Full of jellyfish. Anand Varma, National Geographic, "Episode 8: How I Learned to Love Zombie Parasites," 4 Aug. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'jellyfish.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of jellyfish

1818, in the meaning defined at sense 1a

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Time Traveler for jellyfish

Time Traveler

The first known use of jellyfish was in 1818

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Statistics for jellyfish

Last Updated

24 Oct 2020

Cite this Entry

“Jellyfish.” Dictionary, Merriam-Webster, Accessed 25 Oct. 2020.

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How to pronounce jellyfish (audio)

English Language Learners Definition of jellyfish

: a sea animal that has a very soft body and that can sting


jel·​ly·​fish | \ ˈje-lē-ˌfish How to pronounce jellyfish (audio) \

Kids Definition of jellyfish

: a free-swimming sea animal related to the corals that has a nearly transparent jellylike body shaped like a saucer and tentacles with stinging cells


jel·​ly·​fish | \ ˈjel-ē-ˌfish How to pronounce jellyfish (audio) \

Medical Definition of jellyfish

: a free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells

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