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
According do stylist Kathe Swanson, Courtney Love had to have a special hairpiece pinned to her crown to give her blond mane length & fullness for the "Man In The Moon" movie.