Also known as: 四暗刻
One of the yakuman (highest-scoring) hands in Mahjong. Known in English as "Four Concealed Triplets".
Comes in two variants: suuankou-shanpon, where three of the triplets are in the hand, the wait is on a tile to complete either of the two remaining pairs, and you have to complete that set wait yourself to count as suuankou (lest it'll count only as toitoihou and san'ankou, plus whatever extra value the tiles/hand have); and suuankou-tanki (occasionally valued as double yakuman), where the four triplets are in the hand, the wait is on a single tile to complete the pair, and you can complete that single wait from another player yet it'll still count as suuankou.