A tan line is a visually clear division on the human skin between an area of pronounced comparative
A tan line is a visually clear division on the human skin between an area of pronounced comparative paleness relative to other areas that have been suntanned by exposure to ultraviolet (UV) radiation. The source of the radiation may be the sun, or artificial UV sources such as tanning lamps.Oh my, Wikipedia, really? via wade-garrett-stuff -- source link