Used as a verb it means to bleach the hair and remove current color.
When used as a noun it refers to the chemical composition designed to remove color from the hair. Bleach is sometimes referred to as a pre-lightening or decolorizing treatment.
Daily Hair Tip
A good volumizing trick is to mix equal parts of hair mousse and gel together and then paint sparingly on the roots of your hair before blow drying with a make-up brush.