n. any luminous winged insect, as luminous beetles of the family Lampyridae
It is sort of emission of visible light by living organisms such as the firefly and various fish, fungi, and bacteria.
Sentence in Classic:
They are a tall, strong youth and their eyes are like fireflies, for there is laughter in their eyes.
They seemed to swarm over the place all at once, till the lamplight, shining on their moving dark bodies and glittering, baleful eyes, made the place look like a bank of earth set with fireflies.
His audience heard him with varying emotions, for all who sat there rocking quietly in the fading twilight, watching the first fireflies of the season moving magically through the dusk, had weighty matters on their minds.
Gone With The Wind By Margaret Mitche Context