also: チンイチ
noun
In mahjong, a hand consisting entirely of tiles from one suit with no honor tiles. Often used in the context of a meld or a winning hand.
from Chinese
See also: 清一色
彼は清一で上がった。
He won with a flush.
清一を狙うなら、早めに他のスーツを捨てるべきだ。
If you're aiming for a flush, you should discard tiles of other suits early.
清一色 is the full Chinese-derived term for the same concept; 清一 is a common abbreviation used in Japanese mahjong.
Abbreviation of 清一色 (チンイーソー), from Chinese 清一色 (qīngyīsè), literally 'pure one color'.