The act of hitting someone in the head with a foam weapon.
Shield contact to the head or body is often refered to as Smiting, and is discouraged by the Book of War.
Rocks (Class 5 Weapons), Javelins (Class 4 Weapons), and Arrows (Class 4 Weapons) are all "head legal" (when thrown or shot) weapons and cause death when making contact with a person's head during combat. These weapon types are designed to be safe for head contact, and are often held to stricter testing by weapons checkers to ensure no black eyes, broken noses or other injury will result from the proper use of these weapons.
Swung and stabbing weapons are not allowed to strike the head, so head shots with any swung or stabbing motion is illegal and also presents a certain level of danger to the person recieving the blow. Because of this, some realms observe a punishment for illegal blows to the head. The punishment ranges from combat death to expulsion from the field. It is recommended that serious infractions such as extreme carelessness, purposeful intent, and lack of control recieve immediate intervention from a field marshal.