Webster's Revised Unabridged Dictionary · 1913

Twilight

Twilight , noun

[Old English twilight, Anglo-Saxon twi- (see Twice) + leóht light; hence the sense of doubtful or half light; compare LG. twelecht, German 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

Twilight , adjective

1.
Seen or done by twilight. — Milton
2.
Imperfectly illuminated; shaded; obscure.
O'er the twilight groves and dusky caves. — Pope