noun
yaku-less tenpai; hand one tile from completion without a valid win condition
In mahjong, a hand that is tenpai (one tile away from winning) but lacks any yaku (winning condition), so it cannot be declared a win even if the needed tile is drawn.
形式聴牌の状態では、あがり牌を引いても和了れない。
In a yaku-less tenpai state, you cannot win even if you draw the winning tile.
初心者は形式聴牌に気づかず、無駄な待ちを続けることがある。
Beginners sometimes fail to notice a yaku-less tenpai and keep waiting uselessly.
Compound of 形式 (formality, form) and 聴牌 (tenpai, 'one tile away from winning'). The term describes a hand that is technically tenpai in form but lacks the substance (yaku) needed to win.