whiten up

(redirected from whitening something up)

whiten up

1. To become or appear whiter. His blond hair began whitening up from being in the sunshine all summer long. Try adding a scoop of baking soda to your clothes or linens if you want them to whiten up.
2. To cause something to become or appear whiter. In this usage, a noun or pronoun can be used between "whiten" and "up." The detergent promises to whiten up your clothes. I want to get a toothpaste that whitens up my teeth.
See also: up

whiten up

v.
1. To become whiter: The towels whitened up when I washed them with bleach.
2. To cause something to become whiter: The dentist whitened up my coffee-stained teeth. This polish will whiten your golf shoes up.
See also: up