A cross-up is a term used in the Street Fighter series and other fighting games to refer to methods of circumventing an opponent's defenses.
Description[]
Cross-ups occur when a character attacks an opponent from behind quick enough that the opponent cannot orient themselves properly in time; a defending player may be 'crossed up' and attempt to block by holding backward on the joystick, which results in them holding it toward the attack instead. The proper defense in this scenario is to hold the joystick in the direction the character is facing.
Cross-ups are often executed via jump-ins with certain attacks that can reach on both the attacker's sides, and 'diving' midair attacks; e.g. the Tatsumaki Zankukyaku, or through use of attacks that pass through foes, e.g. M. Bison's Psycho Crusher; if well-timed, Bison will be on their far side when they become vulnerable, forcing them to "block forward" as with the first example. F.A.N.G's Jumping Heavy Kick is a unique example of an attack built solely for cross-ups, attacking directly behind him with no hitbox in front of him.
Cross-up attacks are viable tools during an opponent's wake-up game. Even if cross-ups are properly blocked, the attacker may find themselves in a favorable enough position to apply pressure with frame traps or to tick-throw them.
In Street Fighter 6, most anti-air attacks are incapable of hitting cross-ups by design, with a handful of exceptions like Rashid's Heavy Spinning Mixer. However, Drive Parries can block both sides while held, letting characters have a universal answer against ambiguous cross-ups.