From Japanese mahjong wiki
Tsumo may have several meanings.
- Tsumo is the act of drawing a tile.
- In paifu (play records) or hand patterns, tsumo may refer to a drawn tile or a winning drawn tile.
- Tsumo is called to declare a win on a self-drawn tile.
- Menzenchin tsumohou is usually shortened to tsumo, referring to the yaku worth 1 han achieved by self-drawing with a closed hand.