firefly
Americannoun
noun
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any nocturnal beetle of the family Lampyridae , common in warm and tropical regions, having luminescent abdominal organs See also glow-worm
-
any tropical American click beetle of the genus Pyrophorus , esp P. noctiluca , that have luminescent thoracic organs
Other Word Forms
Etymology
Origin of firefly
Explanation
Fireflies are flying beetles that glow in the dark. If you gently catch a firefly between your palms, you can watch its light flicker on and off for a while, and then let it go. Depending on where you live, you may call fireflies "lightning bugs" or "glowworms." There are fewer of these light-emitting insects on the planet than there used to be, but you can still find places where they gather in groups at dusk, glowing and flickering like stars. Contrary to their name, fireflies aren't flies, but instead belong to a family of beetles with an amazing ability to produce a luminous light.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Firefly Bio is developing its Firelink degrader antibody conjugate platform for KRAS-driven cancers with limited treatment options.
From The Wall Street Journal • Jun. 8, 2026
J&J on Monday said Firefly is developing its proprietary Firelink degrader antibody conjugate platform, for KRAS-driven cancers, which have limited treatment options with survival measured in months.
From The Wall Street Journal • Jun. 8, 2026
Johnson & Johnson agreed to acquire biotechnology company Firefly Bio for $1 billion in cash, bolstering its oncology pipeline.
From The Wall Street Journal • Jun. 8, 2026
Firefly stock rose 18.8% on Tuesday, but was down Wednesday.
From Barron's • May 26, 2026
The Vonnegut was a heavily modified Firefly-class transport vessel, modeled after the Serenity in the classic Firefly TV series.
From "Ready Player One: A Novel" by Ernest Cline
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
