A baseball term that describes a gesture or verbal signal by coaches, managers or players to communicate in-game strategy and decisions in a manner deliberately secret to the opposing team.
Any sign can be either verbal or non-verbal. A non-verbal sign is usually a short or long gesture, and often manifests as a series of simple to elaborate hand signals. Many common non-verbal signs include patting portions of the body or face in succession, pinching the bill of the cap, or tapping fingers on different locations of the arm. Verbal signs usually manifest as one-word phrases, such as "relay" or "cut-off."
Signs can provide an essential means for teams to keep their strategies hidden. Signs are often delivered by coaches and managers to players on the field, in order to communicate strategic calls or decisions that players are expected to follow. For example, a manager may sign to a batter and runner to execute a hit-and-run play.
Players also use signs to communicate defensive strategies amongst each other. Catchers communicate with pitchers on the mound by displaying fingers below their crouch in order to suggest pitches to the plate. Players in the infield or the outfield will often signal others to cover a base or to inform the team how many outs have been recorded.
Teams will mix numerous gestures together often in order to indicate different signs and to keep them complicated enough to prevent the opposing team from deciphering them. A team that is well-trained in the use of signs can communicate efficiently and quickly, allowing managers to facilitate their strategies better on the field and players to make decisions more easily during play.