A quick wrist shot. Just like with a wrist shot, a player who executes a snapshot will use his wrists to give power to the shot, but he will look to get the puck off his stick more rapidly than with a wrist shot.
The snap shot is similar to a slapshot in that it is quick and it is used to surprise goalies when they are not expecting a shot. Unlike the slapshot though, a when a player is executing a snap shot, his stick does not leave the ice. Snap shots are used often in instances of "high traffic" like when a player is near the opposing net and there are a lot of other bodies in the area. In these situations, the goaltender cannot see the puck clearly because there are many players around him obstructing his view. The goalie's view might be obstructed for a matter of seconds, so it is important to use a quick, accurate shot in those situations in order to score a goal more easily.