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

On Earth, animals such as dolphins, crows and fireflies communicate in ways that are very different from ours. — Rupendra Brahambhatt, Interesting Engineering, 1 Nov. 2026

They have been transformed from fly-by-night fireflies to the next Merck or Eli Lilly . — Jim Cramer, CNBC, 1 Nov. 2026

Pisgah’s emerald forests span 500,000 acres, with landscapes much like the Smokies, including waterfalls, hundreds of trail miles, green peaks, and its own population of sparkly insects—blue ghost fireflies. — Stephanie Vermillion, Travel + Leisure, 19 Oct. 2026

Beginnings can feel energetic and chipper and game, kind of, but endings are fireflies in the dark. — Literary Hub, 6 Oct. 2026

Word History

First Known Use

1655, in the meaning defined above

Rhymes for firefly

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

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