Kimura (Brazilian Jiu-Jitsu), chicken wing/double wristlock (wrestling), or reverse keylock are terms used to specify a medial keylock known in judo as gyaku ude-garami (reverse arm entanglement) or simply as ude-garami. The application is similar to the americana, except that it is reversed. It needs some space behind the opponent to be effective, and can be applied from the side control or guard (or half guard or even full-mount). Contrary to the americana, the opponent's wrist is grabbed with the hand on the same side, and the opposite arm is put behind the opponent's arm, again grabbing the attacker's wrist and forming a figure-four. By controlling the opponent's body and cranking the arm away from the attacker, pressure is put on the shoulder joint, and depending on the angle, also the elbow joint (in some variations the opponent's arm is brought behind their back, resulting in a finishing position resembling that of the hammerlock). The kimura was named after the judoka Masahiko Kimura, who used it to defeat one of the founders of Brazilian Jiu-Jitsu, Hélio Gracie. (from wikipedia)
An inspired and beautifully executed kimura from guard/triangle position by Joe Lauzon
Sakuraba applies a phenomenal standing kimura to take down Renzo Gracie
Here Fedor Emelianenko shows some finer points of applying the keylock.
