1. Generally performed by two males, the cross over involves the first male placing both hands inside his partner's pants - one over the buttocks, and one placed firmly over the groin. The male's partner returns this action, so that both arms cross over. This is typically performed in public, as a statement of pride in one's relationship. Experienced couples often resume walking while performing the cross-over, though this is a difficult technique and not recommended to beginners.
2. A dribbling technique used in basketball to change the dribbling direction quickly.

A fanfiction in which several fandoms interact with one another.

Cross-overs largely involve time travel and interdimensional travel to meld two different fandoms.