firefly
n. countablen. a small beetle that glows with a soft light in the dark. You usually see them flying around on warm summer nights.
n. a nocturnal beetle of the family Lampyridae, characterised by the use of bioluminescence to attract mates or prey.
The children tried to catch a firefly in a glass jar.
As the sun set over the meadow, hundreds of fireflies began to blink in the tall grass.
The rhythmic flashing of the firefly is not merely decorative; it serves as a sophisticated species-specific signal used to locate potential mates in the dense evening foliage.
Endocentric compound of fire + fly, because the insects glow; whence also lightning bug. Compare glow fly, glowworm, and lanternfly.
Commonly referred to as a 'lightning bug' in certain regional dialects of American English.