In hockey, a delayed penalty is a minor penalty in which play is allowed to continue as long as the non-offending team retains possession of the puck. This is done so that the opposing team cannot commit an off the puck infraction and stop an offensive attack already in progress. To indicate a delayed penalty, the referee lifts his arm straight in the air. If the non-offending team manages to score before the penalty takes effect, the penalty is negated.
This rule alllows for a small but interesting part of hockey strategy: since play is dead once the offending team takes possession of the puck, they cannot score during the delayed penalty1. As a result, the non-offending team's goalie will quickly sub out and be replaced by an extra attacker, making the game essentially 6-on-5 for the duration of the delay.
1. The offending team can in fact score on a delayed penalty, but only by having the non-offending team put the puck into their own net. When this happens, it's almost always during an attempt to get the puck to the player on the point (that is, at the blue line) for a shot on goal that misses that player and sails down the length of the ice into the non-offending team's empty net. The penalty is not negated during a goal like this.