jellyfish

noun
jel·​ly·​fish | \ˈje-lē-ˌfish \

Definition of jellyfish 

1a : 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

Illustration of jellyfish

Illustration of jellyfish

jellyfish 1a

Keep scrolling for more

Synonyms & Antonyms for jellyfish

Synonyms

doormat, namby-pamby, pushover, reed, weakling, wimp

Antonyms

stalwart

Visit the Thesaurus for More 

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

According to a study done last year, jellyfish might be older, but that study used genetic analysis and not fossilized evidence. Chris Ciaccia, Fox News, "'Holy Grail' fossil mystery cracked – 558 million-year-old fat reveals earliest known animal," 21 Sep. 2018 Dangling from the brain like the tentacles of a jellyfish, olfactory neurons are the only part of the central nervous system constantly exposed to the outside world. Tim Folger, Discover Magazine, "How Quantum Mechanics Lets Us See, Smell and Touch," 24 Oct. 2018 The jellyfish exhibit is getting funding from New York state and the First Niagara Foundation. Fox News, "Niagara Falls Aquarium begins building jellyfish exhibit," 13 May 2018 Now, in addition to learning about sharks, dolphins, sea turtles, stingrays, jellyfish and more, a trip through the Caribbean Journey showcases flamingos, tropical birds, two sloths, a green iguana and a variety of sea creatures. San Antonio Express-News, "Your best bets for attractions all around Texas," 12 June 2018 Plans call for about 100 jellyfish representing four species. Fox News, "Niagara Falls Aquarium begins building jellyfish exhibit," 13 May 2018 Explore all-new exhibit where family meets giant Pacific octopus, moon jellyfish and Japanese spider crabs. Rasputin Todd, Cincinnati.com, "Things to do this week in Cincinnati: May 7-13," 7 May 2018 One is that there is a population boom among jellyfish and similar creatures about every six years, he was quoted saying. Mark Price, charlotteobserver, "One of the world's top beaches is a 'blue carpet of slime' after creatures wash ashore," 2 May 2018 During the day, the upside-down jellyfish Cassiopea pulses about once a second. Michael Greshko, National Geographic, "Brainless Creatures Can Do Some Incredibly Smart Things," 21 May 2018

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.

See More

First Known Use of jellyfish

1841, in the meaning defined at sense 1a

Keep scrolling for more

Learn More about jellyfish

Statistics for jellyfish

Last Updated

8 Dec 2018

Look-up Popularity

Time Traveler for jellyfish

The first known use of jellyfish was in 1841

See more words from the same year

Keep scrolling for more

More Definitions for jellyfish

jellyfish

noun

English Language Learners Definition of jellyfish

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

jellyfish

noun
jel·​ly·​fish | \ˈje-lē-ˌfish \

Kids Definition of jellyfish

: 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

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

Keep scrolling for more

More from Merriam-Webster on jellyfish

Rhyming Dictionary: Words that rhyme with jellyfish

Thesaurus: All synonyms and antonyms for jellyfish

Spanish Central: Translation of jellyfish

Nglish: Translation of jellyfish for Spanish Speakers

Britannica.com: Encyclopedia article about jellyfish

Comments on jellyfish

What made you want to look up jellyfish? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

living or existing for a long time

Get Word of the Day daily email!

Test Your Vocabulary

Late Autumn 2018 Words of the Day Quiz

  • frosted-autumn-leaves
  • Which is a synonym of yahoo?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!