(n.) a person who has dyed his or her hair black (see bottle blonde). The term comes from the fact that hair dye comes in bottles.
She's a bottle black, but her hair is still pretty.
noun. Used to refer to a person with unnaturally black hair. The name comes from the fact that they dye their hair, presumably with something that came from a bottle.
Can also be used in a derogatory manner.
The opposite of bottle blonde.
Girl 1: Look at her roots! She's a total bottle black.