Definition of "Crossover" :

noun: a path (often marked) where something (as a street or railroad) can be crossed to get from one side to the other

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

"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