Definitions of crossover:

• noun:   the appropriation of a new style (especially in popular music) by combining elements of different genres in order to appeal to a wider audience

  Example: "A jazz-classical crossover album"

• noun:   a voter who is registered as a member of one political party but who votes in the primary of another party
• noun:   the interchange of sections between pairing homologous chromosomes during the prophase of meiosis
• noun:   a path (often marked) where something (as a street or railroad) can be crossed to get from one side to the other