In baseball, an out occurs when the umpire rules a batter or baserunner out. When a batter or runner is out, they lose their ability to score a run and must return to the dugout until their next turn at bat. When three outs are recorded in a half-inning, the batting team's turn expires.
To signal an out, an umpire generally makes a fist with one hand, and then flexes that arm either upward, particularly on pop flies, or forward, particularly on routine plays at first base. Home plate umpires often use a "punch-out" motion to signal a called strikeout.