The kimura (reverse ude garami) is a shoulder lock applied by gripping your own wrist around the opponent's wrist, creating a figure-four control. You then rotate the arm in an arc behind their back until the shoulder reaches its limit. The lock targets the rotator cuff and shoulder joint.
It is named after Masahiko Kimura, who used it to defeat Hélio Gracie in 1951 — a famous moment in BJJ history that the Gracie family commemorated by naming the lock after its user.
The kimura is applied from closed guard, side control, turtle, and north-south. In many positions it also functions as a control handle to sweep, take the back, or transition even when the finish is defended. The "kimura trap" system uses the grip as a primary control mechanism throughout a position.
For the guard version, see Kimura from Closed Guard.