jellyfish

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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 cellsb : siphonophorec : 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

Sea lice Irritating rash is seldom harmful Sea lice are not insects but baby thimble jellyfish.

— bonnie berkowitz, chicagotribune.com, "10 creatures that can ruin your day at the beach", 30 June 2017
In this video, shot by marine biologist Johnny Gaskell, a young green sea turtle munches on a jellyfish in the shallow waters around Hook Island, Queensland, in Australia’s famous Great Barrier Reef.

— rachel brown, National Geographic, "Watch: Sea Turtle Snacks on Jellyfish Tentacles", 27 June 2017
Most of the Gulf is a barren desert, empty sand and little else but jellyfish and starfish.

— AL.com, "Alabama's 60,000-year-old underwater forest spills its secrets in new documentary", 25 June 2017
Now her colleagues will crochet 700+ jellyfish for preemies in her memory At first, the experts in Fort Wayne diagnosed the lesion as a cancerous mole.

— shari rudavsky, Indianapolis Star, "'1 in a million, 1 in a billion': Indiana toddler who was born with metastatic melanoma", 19 June 2017
Hear a silly story and create a colorful jellyfish, 10-11 a.m., P.C. Grommetts, Pacific City, 21034 PCH.

— greg mellen, Orange County Register, "Hot summer on tap at Surf City: Here’s what’s going on", 18 June 2017
Their journey through the ocean includes sharks, sea turtles, jellyfish and other sea creatures.

— kara haar, The Hollywood Reporter, "From 'On Golden Pond' to 'Mrs. Doubtfire': 11 Movies for Dads and Their Kids to Watch on Father's Day", 16 June 2017
In addition to sea life such as sharks and jellyfish, there is hyperthermia (too cold) and hypothermia (overheating), waves, currents and the mental stamina required to stay focused and avoid panic.

— deborah brunswick, CNN, "South Africa's siren call to the 'wild' open-water swimmer", 16 June 2017
Follicle stimulating hormone (FSH), like other hormones produced in the pituitary, is ancient; it is evolutionarily conserved and found even in organisms like jellyfishes, corals, and sea anemones.

— diana gitig, Ars Technica, "This one weird antibody reduces belly fat (in post-menopausal women)", 1 June 2017

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

JELLYFISH Defined for English Language Learners

jellyfish

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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

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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

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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