Definition of "firefly"
firefly
noun
plural fireflies
Any beetle of the family Lampyridae, which exhibit bioluminescence during twilight.
Quotations
Various other luciferase genes, especially the firefly luciferase gene, are also used for the study of gene regulation. […] The classic use of bioluminescence, however, is the use of a luciferin-luciferase mixture from fireflies as an assay for ATP.
2007, Lars Olof Björn, Helen Ghiradella, “23: Bioluminescence”, in Lars Olof Björn, editor, Photobiology: The Science of Life and Light, 2nd edition, Springer, page 607