‖n. [ L. nyctalopia, fr. nyctalops a nyctalops, Gr. nykta`lwps. Gr. nykta`lwps meant, a person affected either with day blindness or with night blindness, and in the former case was derived fr. ny`x, nykto`s, night + 'w`ps, 'wpo`s, the eye; in the latter, fr. ny`x + 'alao`s blind + 'w`ps. ] (Med.) (a) A disease of the eye, in consequence of which the patient can see well in a faint light or at twilight, but is unable to see during the day or in a strong light; day blindness. (b) See Moonblink. [ 1913 Webster ]

☞ Some writers (as Quain) use the word in the opposite sense, night blindness. See Hemeralopia. [ 1913 Webster ]