Twi″light′ (?), n. [OE. twilight, AS. twi- (see Twice) + leóht light; hence the sense of doubtful or half light; cf. LG. twelecht, G. zwielicht. See Light.]
1. The light perceived before the rising, and after the setting, of the sun, or when the sun is less than 18° 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.