firefly

noun

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
That’s harder than trying to spot a firefly right next to someone flashing their high-beams at you. — Noah Haggerty, Los Angeles Times, 28 Aug. 2026 North Carolina is also home to synchronous fireflies, another bioluminescent species that lights up on land. — Charlotte Observer, 12 Aug. 2026 The menu might include ingredients like barracuda wrapped in seaweed, bioluminescent firefly squid, or Wagyu beef, a nod to the region but sourced in Japan. — Erika Ebsworth-Goold, Midwest Living, 3 Aug. 2026 As a just-enjoy-the-firefly-without-trying-to-capture-it-for-Instagram deal. — Steven Zeitchik, HollywoodReporter, 28 July 2026 See All Example Sentences for firefly

Word History

First Known Use

1655, in the meaning defined above

Time Traveler
The first known use of firefly was in 1655

Rhymes for firefly

See All Rhymes for firefly

Browse Nearby Words

fireflower
firefly
firefly squid
See all Nearby Words

Cite this Entry

“Firefly.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/firefly. Accessed 1 Sep. 2026.

Copy Citation

Kids Definition

firefly

noun
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

Britannica.com: Encyclopedia article about firefly

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See More

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

Is it 'nerve-racking' or 'nerve-wracking'?

What's the difference between 'fascism' and 'socialism'?

Why does English have so many silent letters?

7 Pairs of Commonly Confused Words
See More

Popular in Wordplay

See More

Ye Olde Nincompoop: Old-Fashioned Words for 'Stupid'

14 Phobias You Probably Haven't Heard Of

Even More Words That Sound Like Insults But Aren't

Even More Bird Names that Sound Like Insults (and Sometimes Are)

12 Lovely and Unusual Words for the Natural World
See More

Popular

See More

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

Ye Olde Nincompoop: Old-Fashioned Words for 'Stupid'

14 Phobias You Probably Haven't Heard Of
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
skateboard-dog-hat
Wordmaxxing Slang Quiz Give your vocabulary a glow up by getting sendy w...
See All