jellyfish

noun

jel·​ly·​fish ˈje-lē-ˌfish How to pronounce jellyfish (audio)
Synonyms of jellyfishnext
1
a
: 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)
b
: siphonophore
c
: ctenophore
2
: a person lacking backbone or firmness

Illustration of jellyfish

Illustration of jellyfish
  • jellyfish 1a

Synonyms of 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
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Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The time is right, but the weather might not cooperate as SpaceX has lined up a predawn launch Monday that could offer viewers another serving of space jellyfish. — Richard Tribou, The Orlando Sentinel, 18 Oct. 2026 The whale’s gullet is flickeringly lit by a bioluminescent jellyfish that Jay sort of befriends. — Amy Nicholson, Los Angeles Times, 15 Oct. 2026 SpaceX launched a cargo mission to the International Space Station before dawn Tuesday that brought a sonic boom and a space jellyfish effect to the skies over Central Florida. — Richard Tribou, Chicago Tribune, 13 Oct. 2026 While jellyfish, an even more remote species, have two nervous systems, the findings suggest these two organs may have slowly grown close to each other. — Victor Tangermann, Futurism, 24 Sep. 2026 See All Example Sentences for jellyfish

Word History

First Known Use

1818, in the meaning defined at sense 1a

Time Traveler
The first known use of jellyfish was in 1818

Phrases Containing jellyfish

Rhymes for jellyfish

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Browse Nearby Words

jelly end rot
jellyfish
jelly fungus
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Cite this Entry

“Jellyfish.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/jellyfish. Accessed 20 Oct. 2026.

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Kids Definition

jellyfish

noun
jel·​ly·​fish ˈjel-ē-ˌfish How to pronounce jellyfish (audio)
1
: any of numerous free-swimming coelenterate animals that reproduce sexually and have a jellylike, saucer-shaped, and usually nearly transparent body and tentacles with stinging cells
2
: any of various sea animals that resemble a jellyfish

Medical Definition

jellyfish

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

More from Merriam-Webster on jellyfish

Britannica.com: Encyclopedia article about jellyfish

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