When a team or player shoots the puck into the offensive zone before they cross the blue line in order to get a line change or play dump and chase hockey.
Although it sounds pretty simple, there are numerous kinds of dump-ins that if well executed could lead to offensive scoring chances or burning time off the clock as a defensive move.
For example, teams can do cross-corner dump-ins, or hard wrap-around-the-net dump ins or soft-corner dump-ins depending on the pressure teammates can put on the other team, or how much time is needed to get all the players off the ice for the line change.
Since 2005, goaltenders have not been able to play the puck in the corners outside the trapezoid. This has meant teams have tried more corner dump-ins when they want to pursue the puck. Most commonly, you will see dump-ins when teams need to go off for a line change.
Occasionally goaltenders can misplay dump-ins that go off stanchions or redirect awkwardly behind the net. Goalies usually try to stop wrap-around-the-net dump-ins to set the puck up for their defensemen.
One of the most famous goals scored off a dump-in was in game three of the 1975 Stanley Cup Final when Buffalo's Rene Robert raced after a cross-corner dump-in and fired the puck past Flyers' netminder Bernie Parent in what was forever known as the Fog Game due to the thick fog that delayed and stopped the game throughout the night in Buffalo's Memorial Auditorium.