n. [ Cf. F. phosphorescence. ] 1. The quality or state of being phosphorescent. [ 1913 Webster ]
2. The process of phosphorescing, especially that of emitting light after a source of excitation has been removed. This contrasts with the process of fluorescence, in which a substance emits light of a lower wavelength than the illuminating light, only while the illumination continues. [ PJC ]
3. Light emitted by the process of phosphorescence. [ 1913 Webster ]