firefly

American  

[fahyuhr-flahy] / ˈfaɪərˌflaɪ /

noun

plural

fireflies

1. any nocturnal beetle of the family Lampyridae, characterized by a soft body with a light-producing organ at the rear of the abdomen.

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firefly British  

/ ˈfaɪəˌflaɪ /

noun

1. any nocturnal beetle of the family Lampyridae , common in warm and tropical regions, having luminescent abdominal organs See also glow-worm

2. any tropical American click beetle of the genus Pyrophorus , esp P. noctiluca , that have luminescent thoracic organs

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Etymology

Origin of firefly

First recorded in 1650–60; fire + fly ¹

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

To simulate microgravity, researchers used a 3D clinostat machine developed by Dr. Giles Kirby at Firefly Biotech.

From Science Daily • Mar. 29, 2026

The stock prices of rocket makers Firefly Aerospace and Rocket Lab rose by more than 10%, while other space-related firms also saw their shares jump.

From BBC • Mar. 25, 2026

Firefly Aerospace jumps following the successful launch of the Alpha Flight 7 mission on Wednesday.

From Barron's • Mar. 12, 2026

Adobe has integrated third-party AI models into existing products such as Photoshop and Premiere Pro, and launched its own AI product, Firefly.

From The Wall Street Journal • Mar. 12, 2026

The insects were diminishing in number, and soon their season would be over, which was just as well, as the Fentress Firefly Prize ribbon was grubby and limp.

From "The Evolution of Calpurnia Tate" by Jacqueline Kelly