Firefly \Fire"fly`\, n.; pl. Fireflies. (Zo["o]l.) Any luminous winged insect, esp. luminous beetles of the family Lampyrid[ae].

Note: The common American species belong to the genera Photinus and Photuris, in which both sexes are winged. The name is also applied to luminous species of Elaterid[ae]. See Fire beetle.

Source: Webster's Revised Unabridged Dictionary (1913)