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

For example, bumble bee queens, firefly larvae, and some species of lady beetles and wasps overwinter in leaf litter. —Anne Readel, Better Homes & Gardens, 3 Mar. 2026

Its misty mountains are mesmerizing and home to all kinds of plants and wildlife, including fireflies that synchronize for a few weeks each year. —Eve Chen, USA Today, 1 Mar. 2026

And now, a top that is nothing more than a giant sculptural firefly. —Meg Walters, InStyle, 21 Feb. 2026

There’s an underground river in Bowling Green, Kentucky, and synchronous fireflies to see in the Smokies. —Tara Massouleh McCay, Southern Living, 15 Feb. 2026

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