jellyfish

noun jel·ly·fish \ ˈje-lē-ˌfish \

|Updated on: 18 Aug 2018

Definition of jellyfish

1 a : 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

b : siphonophore

c : ctenophore

2 : a person lacking backbone or firmness

See jellyfish defined for English-language learners

See jellyfish defined for kids

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 of jellyfish from the Web

There were enormous violet starfish, and fried egg jellyfish, big enough to fill a skillet.

— matthew kronsberg, WSJ, "An Unmissable Outdoor Adventure in Canada’s Gulf Islands," 21 June 2018
The baby jellyfish float by every year during the summer months.

— National Geographic, "What's Giving Some Beachgoers Rashes? Get the Facts.," 28 June 2018
Health officials stress that these jellyfish larvae are not related to head lice, which are common among young children and can be quite contagious.

— amanda macmillan, Health.com, "What Are Sea Lice, and How Do You Avoid Their Red, Itchy Rash?," 27 June 2018
The critters go by other names including thimble jellyfish, and their sting can cause nasty side effects like a rash, itching, and other cumbersome symptoms.

— sy mukherjee, Fortune, "What You Should Know About These Nasty, Rash-Causing Sea Lice Reported in Florida Beaches," 27 June 2018
According to the Florida Department of Health, sea lice, also called thimble jellyfish, can cause dermatitis, or small red bumps on a person's skin.

— caitlin o'kane, CBS News, "Sea lice reported on Florida beach," 27 June 2018
Clear and present danger: tiny, translucent, poisonous jellyfish have decided to spend another summer at the Jersey Shore, PhillyVoice says.

— oona goodin-smith, Philly.com, "Your guide to the Fourth in Philly, study finds city hiring slow | Morning Newsletter," 27 June 2018
In this case, Moon jellyfish are largely to blame for the stings.

— madeline farber, Fox News, "Jellyfish stings causes hundreds of Florida beachgoers to be treated," 13 June 2018
But the footage speaks for itself with holographic screens that include totally readable text, 3D displays, and swarms of floating jellyfish.

— eric limer, Popular Mechanics, "New Footage From Magic Leap Is a Thrilling Glimpse of the Future," 19 Apr. 2016

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'jellyfish.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Illustration of jellyfish

First Known Use of jellyfish

1841

in the meaning defined at sense 1a

See Words from the same year

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jellyfish Synonyms

JELLYFISH Defined for English Language Learners

jellyfish

noun

Definition of jellyfish for English Language Learners

: a sea animal that has a very soft body and that can sting

JELLYFISH Defined for Kids

jellyfish

noun jel·ly·fish \ ˈje-lē-ˌfish \

Definition of jellyfish for Students

: a free-swimming sea animal related to the corals that has a nearly transparent jellylike body shaped like a saucer and tentacles with stinging cells

Medical Dictionary

jellyfish

noun jel·ly·fish \ ˈjel-ē-ˌfish \

medical Definition of jellyfish

: 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