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
How did the jellyfish turn into a squid?
—
Matthew Wills, JSTOR Daily, 3 Apr. 2026
These include cnidarians, a group of radially symmetric organisms including present-day jellyfish.
—ArsTechnica, 2 Apr. 2026
Sea turtles and other marine animals can often confuse burst balloons floating in the water for jellyfish.
—Stephen Underwood, Hartford Courant, 31 Mar. 2026
Many of Deguchi’s jellyfish spawned daily, releasing their eggs and sperm into the water, usually shortly after sunrise.
—Marlowe Starling, Quanta Magazine, 20 Mar. 2026
See All Example Sentences for jellyfish
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Matthew Wills, JSTOR Daily, 3 Apr. 2026
These include cnidarians, a group of radially symmetric organisms including present-day jellyfish.
—ArsTechnica, 2 Apr. 2026
Sea turtles and other marine animals can often confuse burst balloons floating in the water for jellyfish.
—Stephen Underwood, Hartford Courant, 31 Mar. 2026
Many of Deguchi’s jellyfish spawned daily, releasing their eggs and sperm into the water, usually shortly after sunrise.
—Marlowe Starling, Quanta Magazine, 20 Mar. 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 10 Apr. 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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