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
When blow drying hair always apply a protective leave in conditioner and hold nozzle at least 6 inches away from your scalp. Dry on lowest, coolest setting for extra protection.