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.
- The diffused light from the sky during the early evening or early morning when the sun is below the horizon and its light is refracted by the earth's atmosphere.
- The time of the day when the sun is just below the horizon, especially the period between sunset and dark.
- Dim or diffused illumination.
- A period or condition of decline following growth, glory, or success: in the twilight of his life.
- A state of ambiguity or obscurity.