Stumped is a method of dismissing a batsman in cricket, which involves the wicket-keeper putting down the wicket while the batsman is out of his ground. (The batsman leaves his ground when he has moved down the pitch beyond the popping crease, usually in an attempt to hit the ball). The action of stumping can only be performed by a wicket-keeper, and can only occur from a legitimate delivery (i.e. not a no-ball), while the batsman is not attempting a run; it is a special case of a run out.
Being "out of his ground" is defined as not having any part of the batsman's body or his bat touching the ground behind the crease – i.e., if his bat is slightly elevated from the floor despite being behind the crease, or if his foot is on the crease line itself but not completely across it and touching the ground behind it, then he would be considered out (if stumped). One of the fielding team (such as the wicket-keeper himself) must appeal for the wicket by asking the umpire. The appeal is normally directed to the square-leg umpire, who would be in the best position to adjudicate on the appeal.