also: うらスジ
noun
urasuji; side fork
Mahjong term for a specific tile arrangement or discard pattern; the English gloss 'urasuji' is often used by English-speaking players.
裏スジを読んで相手の待ちを推測する。
Read the urasuji to guess the opponent's wait.
noun
frenulum; frenulum of prepuce of penis
Colloquial term for the frenulum, especially the penile frenulum; used in informal or sexual contexts.
裏筋が切れると痛いらしい。
I hear it hurts when the frenulum tears.
Compound of 裏 (ura, 'back, reverse') and 筋 (suji, 'line, tendon'). The mahjong sense derives from the idea of a 'reverse line' in tile discards. The anatomical sense is a metaphorical extension referring to the frenulum as a 'back tendon'.