Noah Webster's New International Dictionary of the English Language
1. (v. i.) To descend; to light.
2. (v. i.) To burst forth or dart, as lightning; to shine with, or like, lightning; to display a flash or flashes of lightning; to flash.
3. (v. i.) To grow lighter; to become less dark or lowering; to brighten; to clear, as the sky.
4. (v. t.) To make light or clear; to light; to illuminate; as, to lighten an apartment with lamps or gas; to lighten the streets.
5. (v. t.) To illuminate with knowledge; to enlighten.
6. (v. t.) To emit or disclose in, or as in, lightning; to flash out, like lightning.
7. (v. t.) To free from trouble and fill with joy.
8. (v. t.) To make lighter, or less heavy; to reduce in weight; to relieve of part of a load or burden; as, to lighten a ship by unloading; to lighten a load or burden.
9. (v. t.) To make less burdensome or afflictive; to alleviate; as, to lighten the cares of life or the burden of grief.
10. (v. t.) To cheer; to exhilarate.