noun
atamahane; head bump rule
A mahjong house rule: when multiple players declare a win on the same discard, the player closest in turn order to the discarder wins. The term literally means 'head jump' or 'head bump', reflecting the idea of jumping ahead of others.
この雀荘では頭ハネを採用している。
This mahjong parlor uses the atamahane rule.
頭ハネがあるから、上家がロンを宣言したら自分は
Because of the head bump rule, if the player before me declares ron, I can't win.
Compound of 頭 (atama, 'head') and 跳ね (hane, 'jump/bump'), from the verb 跳ねる (haneru). The term describes the 'jumping' of the win to the player closest in turn order.