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
Billie Eilish and Miley Cyrus followed suit with their own twists on the jellyfish.
—
Anna Cafolla, Vogue, 7 Feb. 2025
The jellyfish cut also sees a drastically shorter layer, but it is cut all the way around the head, while the hime cut only has the front pieces cut.
—Hedy Phillips, People.com, 6 Feb. 2025
But unlike jellyfish, which drift and swim in ocean currents, V. velella are at the mercy of the wind.
—Margherita Bassi, Smithsonian Magazine, 8 Apr. 2025
For example, green fluorescent protein, which was discovered in jellyfish, is today used in medical studies to illuminate stages of embryological development and to reveal the growth of cancers and other types of cells.
—Mindy Weisberger, CNN, 20 Feb. 2025
See All Example Sentences for jellyfish
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Anna Cafolla, Vogue, 7 Feb. 2025
The jellyfish cut also sees a drastically shorter layer, but it is cut all the way around the head, while the hime cut only has the front pieces cut.
—Hedy Phillips, People.com, 6 Feb. 2025
But unlike jellyfish, which drift and swim in ocean currents, V. velella are at the mercy of the wind.
—Margherita Bassi, Smithsonian Magazine, 8 Apr. 2025
For example, green fluorescent protein, which was discovered in jellyfish, is today used in medical studies to illuminate stages of embryological development and to reveal the growth of cancers and other types of cells.
—Mindy Weisberger, CNN, 20 Feb. 2025
See All Example Sentences for jellyfish
Cite this Entry
“Jellyfish.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/jellyfish. Accessed 28 May. 2025.
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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