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
Watch huge jellyfish make appearance on Maine beach Jellyfish warnings issued
Several coastal communities in Maine issued a jellyfish warning as there has been an increase in sightings of lion’s mane and moon jellyfish, according to local station Fox 23 Maine.
—
Julia Gomez, USA Today, 27 June 2025
In addition, lifeguards often have access to real-time information about water quality, tides, jellyfish blooms and other hazards that the average beachgoer wouldn’t otherwise be aware of.
—Scott Travers, Forbes.com, 21 June 2025
The room, decorated with an under-the-sea theme, had a balloon arch decked out with streamers meant to look like jellyfish and a cloud of clear balloons mimicking ocean bubbles.
—Lydia McFarlane, Miami Herald, 12 June 2025
Cocoa Kayaking and Adventure Kayak of Cocoa Beach lead a variety of expeditions, including mangrove tours through the Thousand Islands and nighttime trips to see bioluminescent jellyfish.
—Lisa Cericola, Southern Living, 8 June 2025
See All Example Sentences for jellyfish
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Julia Gomez, USA Today, 27 June 2025
In addition, lifeguards often have access to real-time information about water quality, tides, jellyfish blooms and other hazards that the average beachgoer wouldn’t otherwise be aware of.
—Scott Travers, Forbes.com, 21 June 2025
The room, decorated with an under-the-sea theme, had a balloon arch decked out with streamers meant to look like jellyfish and a cloud of clear balloons mimicking ocean bubbles.
—Lydia McFarlane, Miami Herald, 12 June 2025
Cocoa Kayaking and Adventure Kayak of Cocoa Beach lead a variety of expeditions, including mangrove tours through the Thousand Islands and nighttime trips to see bioluminescent jellyfish.
—Lisa Cericola, Southern Living, 8 June 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 8 Jul. 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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