fire·fly | \ˈfī(-ə)r-ˌflī \

Definition of firefly 

: 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

Illustration of firefly

Examples of firefly in a Sentence

Recent Examples on the Web

There were also fireflies everywhere on the big lawn, which the children chased around all evening once the weather cleared. Fortune, "'Glamping' Has Officially Come to New York City," 12 July 2018 Nothing more than a gentle breeze stirs the air, as fireflies dance and occasional growls emanate from the storm cloud. Matthew Cappucci, Washington Post, "Bolts from the blue: Here’s how lightning can strike when a storm is tens of miles away," 27 June 2018 Both males and females flicker, and every species of firefly has evolved a unique code to help potential mates cut through the noise. Katherine J. Wu, Smithsonian, "Why Bioluminescence Evolved to Be Red Light, and Blue," 26 June 2018 Plant Native Pine Trees One of the biggest threats to fireflies is habitat loss. Rebecca Straus, Good Housekeeping, "6 Ways To Attract Fireflies To Your Yard," 9 June 2016 This is akin to how a firefly or a glow-stick generates its light. Kevin Davenport, idahostatesman, "O say can you see? The science behind the booms and blooms of Independence Day fireworks," 3 July 2018 These glowing bugs tend to be called fireflies in the South and lightning bugs in the Midwest. Kathryn Prociv, Washington Post, "Fireflies photobomb the Milky Way like a mischievous child with neon paint," 22 June 2018 The primary firefly love language is light, and courtship is an appropriately flashy process. Katherine J. Wu, Smithsonian, "Why Bioluminescence Evolved to Be Red Light, and Blue," 26 June 2018 Go in early summer to catch the exceptional synchronous fireflies that light up the night sky for a week or two each year. Megan Michelson, Outside Online, "6 Under-the-Radar National Parks You Should Visit," 20 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'firefly.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of firefly

1655, in the meaning defined above

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Statistics for firefly

Last Updated

12 Sep 2018

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Time Traveler for firefly

The first known use of firefly was in 1655

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More Definitions for firefly



English Language Learners Definition of firefly

: a small flying insect that produces a soft light


fire·fly | \ˈfīr-ˌflī \
plural fireflies

Kids Definition of firefly

: a small beetle producing a soft light

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Comments on firefly

What made you want to look up firefly? Please tell us where you read or heard it (including the quote, if possible).


one that holds something together

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