Shoryuken (昇龍拳, Shōryūken?, "Rising Dragon Fist"), also known as the Dragon Punch in English language media, is a fictional special attack in the Street Fighter series used by Ryu, Ken and other Street Fighter characters trained under the same style. The move is a jumping uppercut in which the user spins, knocking the opponent to the ground.

The Shoryuken is the archetypal "Anti-air" move in two-dimensional fighting games, used to knock opponents out of the sky while dealing heavy damage, with minimal risk to the player. Almost every similar game from the era of sprite based fighting games contain a move similar to the Shoryuken, and in some cases the moves are virtually identical in both performance and execution. During gameplay, the move has a huge priority over other moves. In most cases the player character is completely invincible during the rising portion of the move, and even in games when they are not, the Shoryuken will usually beat any other normal or special move if both are performed at the same time.

Source: Wikipedia