Also found in: Dictionary, Thesaurus, Legal, Financial.
lighten something up
to make something lighter or brighter. Some white paint will lighten this room up a lot. The sunlight came in and lightened up the kitchen.
lighten up (on someone or something)
to be less rough and demanding or rude with someone or something. Please lighten up on her. You are being very cruel. You are too harsh. Lighten up.
to become lighter or brighter. (See also lighten up (on someone or something).) We applied a new coat of white paint to the walls, and the room lightened up considerably. The sky is beginning to lighten up a little.
Become or cause to become less serious or gloomy, and more cheerful. For example, Lighten up, Sam-it'll turn out all right. This slangy expression transfers reducing a physical weight to a change of mood or attitude.
1. To make something appear lighter in shade: The artist lightened up the paint by mixing in some white. Those mirrors really lighten the room up.
2. To become lighter in shade: These pants are too dark now, but they will lighten up after they've been washed a lot.
3. To make something more pleasant and less serious or depressing: The jokes lightened up the tone of the meeting. I didn't mean to be disrespectful—I was just trying to lighten things up.
4. To take matters less seriously: Everything will work out fine, so stop worrying and lighten up.