Reversal

A reversal, sometimes informally referred to as a "wake-up", is a technique in the Street Fighter series and other fighting games, where a player performs a counterattack, often immediately after receiving an attack.

Description
Reversals are performed by inputting the desired attack (anything from a special attack to a Super/Ultra Combo) so that it is performed the very moment the player recovers. This can only occur in the following situations: The window for performing reversals is generally small, and opponents will often try to attack a downed player the moment they get up. As such, reversals are best performed with moves that possess invincibility frames, such as the Shoryuken.
 * Getting up or quick standing after knockdown. The term "wake-up" refers specifically to this kind of reversal.
 * Exiting the blocking state.
 * Landing after being hit in mid-air, provided the hit does not knock the player down.
 * Exiting the stunned state.

Street Fighter IV series
In addition to providing a slightly larger window for reversals, the games also grant reversal attacks Armor Breaking properties. This works well if the opponent attempts to follow up with a charged Focus Attack, for example.