To Lighten

1. (transitive) To make brighter or clearer; to illuminate.
2. (intransitive) To become brighter or clearer; to brighten.
3. (intransitive, archaic) To burst forth or dart, as lightning; to shine with, or like, lightning; to flash.
4. (transitive) To emit or disclose in, or as if in, lightning; to flash out, like lightning.
5. To illuminate with knowledge; to enlighten.