isolated tile
In mahjong, a tile that is not part of any meld or pair and has no adjacent tiles within two ranks to form a sequence; often a lone honor tile or a suited tile separated from other tiles.
See also: 浮き牌
Discard isolated tiles to organize your hand.
This isolated tile doesn't contribute to any yaku, so it's better to discard it early.
Compound of 孤立 (isolated) and 牌 (tile), a straightforward mahjong term.