In basketball, defensive action taken by a team following its offensive possession of the ball, but before it adopts any set defensive positions.
Transition defense is most commonly discussed in terms of a team's ability to transition from offense to defense. Whether possession changed as the result of a score or a turnover, the initial defensive actions taken by a team as they are moving from the front court to the defensive back court are labeled as transition defense. Most strategies involving transition defense involve preventing the opposing team from creating a fast break. Typically this will involve one guard remaining in the front court following a made basket or a turnover, with the rest of the team hustling back to form a defense. Against teams that are particularly skilled at the fast break, teams may keep two guards close to the offense or utilize a full court press defense to slow down the opposing team. Full court presses and halfcourt traps are common uses of transition defense but can also be risky because they can leave the painted area vulnerable and actually sometimes increase the chance of a transition layup.