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