Illustration of jellyfish
- jellyfish 1a
jellyfish
noun
jel·ly·fish
ˈje-lē-ˌfish 
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
c
2
: a person lacking backbone or firmness
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
Among these phenomena are discoveries around previously unknown and merging galaxies, including some that are jellyfish-shaped and several that researchers can’t fit into existing classifications.
—
Rachyl Jones, semafor.com, 28 Jan. 2026
Among the species discovered were ancient relatives of worms, sponges and jellyfish.
—CBS News, 28 Jan. 2026
The dress and outfit were inspired by her daughter Shai’s love of jellyfish, while some details in the accessories, designed by couturier Robert Wun, referenced a butterfly landing on Osaka’s face at the 2021 Australian Open.
—Charlie Eccleshare, New York Times, 24 Jan. 2026
Researchers found that the jellyfish, which host photosynthetic algae, are active during the day, sleep mainly at night, and even take midday naps, much like some humans do after lunch.
—New Atlas, 24 Jan. 2026
See All Example Sentences for jellyfish
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Rachyl Jones, semafor.com, 28 Jan. 2026
Among the species discovered were ancient relatives of worms, sponges and jellyfish.
—CBS News, 28 Jan. 2026
The dress and outfit were inspired by her daughter Shai’s love of jellyfish, while some details in the accessories, designed by couturier Robert Wun, referenced a butterfly landing on Osaka’s face at the 2021 Australian Open.
—Charlie Eccleshare, New York Times, 24 Jan. 2026
Researchers found that the jellyfish, which host photosynthetic algae, are active during the day, sleep mainly at night, and even take midday naps, much like some humans do after lunch.
—New Atlas, 24 Jan. 2026
See All Example Sentences for jellyfish
Cite this Entry
“Jellyfish.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/jellyfish. Accessed 2 Feb. 2026.
Copy CitationKids Definition
jellyfish
noun
jel·ly·fish
ˈjel-ē-ˌfish
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
: 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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