fire·​fly ˈfī(-ə)r-ˌflī How to pronounce firefly (audio)
: 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 With eight lighting modes — fireflies flashing, waves/fading, chasing, flashing, fading slowly, twinkling, flashing, and steady on — this decorative 100-LED rope light will add charm and ambiance to your home all year long. Katie Begley, Peoplemag, 10 Nov. 2023 Indian photographer and dark sky advocate Sriram Murali captured this ethereal light, emitted by fireflies, through a series of 50 long exposures, each lasting 19 seconds. Carlyn Kranking, Smithsonian Magazine, 12 Oct. 2023 While the traditional preparations are superb — including achingly good Dungeness crab and tender firefly squid — Mr. Tsukasaki is also expanding the Edomae sushi vocabulary with dishes like lean tuna belly with housemade soy milk and shio koji. Melissa Clark, New York Times, 18 Sep. 2023 Featuring an ancient horseshoe crab, fighting ibex and a forest lit by fireflies’ glow, the winners of the 59th annual Wildlife Photographer of the Year contest reveal breathtaking scenes of animals and their fascinating behaviors. Carlyn Kranking, Smithsonian Magazine, 12 Oct. 2023 Light pollution is another big detriment to these and many night-active insects (like fireflies). Miri Talabac, Baltimore Sun, 18 July 2023 Recreate some of that wonder on a summer night by catching fireflies in a jar and briefly observing them before setting them free. Jenny McCoy, SELF, 27 June 2023 The firefly and bacterial genes just didn’t work well in plants. WIRED, 19 Sep. 2023 It’s created by a chemical reaction within organisms such as algae, bacteria, jellyfish, fish, fireflies and even fungus. Mark Graves | , oregonlive, 11 Aug. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'firefly.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1655, in the meaning defined above

Time Traveler
The first known use of firefly was in 1655

Dictionary Entries Near firefly

Cite this Entry

“Firefly.” Dictionary, Merriam-Webster, Accessed 7 Dec. 2023.

Kids Definition


fire·​fly ˈfī(ə)r-ˌflī How to pronounce firefly (audio)
: any of numerous night-flying beetles that produce a bright soft flashing light for courtship purposes

More from Merriam-Webster on firefly

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