firefly

noun

fire·​fly ˈfī(-ə)r-ˌflī 

: any of various winged nocturnal beetles (especially family Lampyridae) that produce a bright soft intermittent light by oxidation of luciferin especially for courtship purposes

Illustration of firefly

Examples of firefly in a Sentence

Recent Examples on the Web

Giant ponderosa pines crashed down around us with little warning, weakened by fire and shooting off embers like fireflies in smoke. —Andony Corleto, Mercury News, 29 July 2025

By Sharon Attia The New York Times S’mores are the dessert equivalent of fireflies and sleeping bags. —The New York Times News Service Syndicate, San Diego Union-Tribune, 16 July 2025

But scientific understanding of fireflies is incomplete. —Connor Giffin, The Courier-Journal, 3 July 2025

New research published in BMC Genomics looks at the genetics of the common eastern firefly (Photinus pyralis) and found that besides bioluminescent flashes, fireflies may also be using pheromones to attract mates. —Monica Cull, Discover Magazine, 18 July 2025

Word History

First Known Use

1655, in the meaning defined above

Rhymes for firefly

• abscissae
• alibi
• alkali
• alumni
• amoebae
• amplify
• annuli
• beautify
• brachii
• butterfly
• calculi
• certify

Kids Definition

firefly

noun

fire·​fly ˈfī(ə)r-ˌflī 

: any of numerous night-flying beetles that produce a bright soft flashing light for courtship purposes