1. The light perceived before the rising, and after the setting, of the sun, or when the sun is less than 18 deg below the horizon, occasioned by the illumination of the earth's atmosphere by the direct rays of the sun and their reflection on the earth.
2. Faint light; a dubious or uncertain medium through which anything is viewed. As when the sun . . . From behind the moon, In dim eclipse. Disastrous twilight sheds. (milton) The twilight of probability. (locke)
Origin: OE. Twilight, AS. Twi- (see Twice) _ leoht light; hence the sense of doubtful or half light; cf. LG. Twelecht, G. Zwielicht. See Light.