also: ツーパイ
noun
honor tiles
In mahjong, the set of tiles representing the three dragons and four winds; distinct from suited tiles.
from Chinese zì pái
字牌は全部で28枚あります。
There are 28 honor tiles in total.
この手は字牌が多くて難しい。
This hand has many honor tiles and is difficult.
Katakana spelling reflecting the Chinese-derived reading; common in mahjong contexts.
数牌 are the suited tiles (man, pin, sō), while 字牌 are the honor tiles (winds and dragons).
From Chinese 字牌 (zì pái), literally 'character tile'.