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

: siphonophore

c

: ctenophore

2

: a person lacking backbone or firmness

Illustration of jellyfish

• jellyfish 1a

Synonyms

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

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

What is the lifespan of the jellyfish? Jellyfish do not live long. —Olivia Munson, USA TODAY, 30 Mar. 2024

Share [Findings] Stinging water was blamed on jellyfish mucus. —Rafil Kroll-Zaidi, Harper's Magazine, 27 Mar. 2024

But the fluorescence of those proteins—originally synthesized from a jellyfish—is visible only with specialized lights, unlike the petunia now in my house, which glowed on its own. —Zoë Schlanger, The Atlantic, 19 Mar. 2024

The winning photo will be on display until June 30 at London’s Natural History Museum, along with finalist images showcasing a sweet moment of lion parenting and glowing moon jellyfish beneath the northern lights. —Ashley Strickland, CNN, 10 Feb. 2024

Isaac’s were stuffed with jellyfish and plum, mine with mustard greens and salmon flakes. —Helen Schulman, Travel + Leisure, 2 Mar. 2024

The water world includes a massive humpback whale that swims above the arena while several jellyfish descend from the rafters. —Bryan West, USA TODAY, 6 Feb. 2024

On the back side of Concord Mills, this new aquarium includes at least 5,000 sea creatures, including jellyfish, sharks and stingrays. —Samantha Sabin -, Charlotte Observer, 31 Jan. 2024

Lantern exhibits will include an underwater tableau complete with jellyfish and a sea turtle, a variety of large animals from the African savannah, an elaborate glowing dragon and more. —Natalie Wallington, Kansas City Star, 26 Jan. 2024

Word History

First Known Use

1818, in the meaning defined at sense 1a

Phrases Containing jellyfish

• box jellyfish

Kids 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