Boarding in ice hockey is a penalty called when an offending player pushes, trips or checks an opposing player violently into the boards (walls) of the hockey rink.
In ice hockey, the boarding call is often a major penalty due to the likelihood of injury sustained by the player who was boarded, and officials have the discretion to call a game misconduct or a match penalty (if they feel the offense was a deliberate attempt to injure) on the offending player.
However, in the North American professional ice hockey league, the NHL, if a major penalty is assessed and the boarded player sustains a head or facial injury, the offending player receives an automatic game misconduct.
If no injury is sustained, then a minor penalty will be called.
In college ice hockey, the player does not need to be injured for it to be a major penalty.