crossover (Noun) — The interchange of sections between pairing homologous chromosomes during the prophase of meiosis.
crossover (Noun) — A voter who is registered as a member of one political party but who votes in the primary of another party.
crossover (Noun) — (music genre) the appropriation of a new style (especially in popular music) by combining elements of different genres in order to appeal to a wider audience. ex. "a jazz-classical crossover album"
crossover (Noun) — A path (often marked) where something (as a street or railway) can be crossed to get from one side to the other.