The Joudan Sokutou Geri (上段足刀蹴り, lit. High-Level Foot Edge Kick) is one of Ryu's special attacks in certain games. The attack is a simple (yet strong) forward-stepping side kick. Ryu steps forward a short distance before delivering a powerful side kick to his opponent that may result in a wall bounce. This attack first showed up in the Street Fighter III series, and was not in his moveset in the Marvel vs. series until MvC3 (though it previously appeared in the Vs. game Tatsunoko vs. Capcom).
In both TvC and MvC3, the move follows its EX version, in that it already provides a wallbounce on hit, making it one of Ryu's best combo tools. However, the attack is a bit slow on startup and can be ducked by a number of crouching opponents, so he often has to use this move in a good combo, or if possible, as an unexpected yet risky poke.