Of or relating to fluorescence. Exhibiting or produced by fluorescence: fluorescent corals; fluorescent light. Glowing as if with fluorescence; vivid: bright fluorescent colors. Of or relating to a light bulb that produces visible light by fluorescence, especially a glass tube whose inner wall is coated with a material that fluoresces when an electrical current causes a vapor within the tube to discharge photons. A fluorescent light bulb. A lamp that is fitted with a fluorescent light bulb.