| 1. | to become lighter or less dark; brighten: The sky lightened after the storm. |
| 2. | to brighten or light up, as the eyes or features: Her face lightened when she heard the good news. |
| 3. | to flash as or like lightning (often used impersonally with it as subject): It thundered and lightened for hours. |
| 4. | Archaic. to shine, gleam, or be bright: steel blades lightening in the sun. |
| 5. | to give light to; illuminate: A full moon lightened the road. |
| 6. | to brighten (the eyes, features, etc.): A large smile lightened his face. |
| 7. | to make lighter or less dark: Add white to lighten the paint. |
| 8. | Obsolete. enlighten. |
| 9. | Obsolete. to flash or emit like lightning (usually fol. by out, forth, or down): eyes that lightened forth implacable hatred. |