three kongs; winning hand with three kongs
A mahjong yaku: a hand that contains three kongs (槓子).
from Chinese sān gàng zi
Three kongs is one of the rare yaku.
He completed a three-kong hand and turned the game around.
槓 is the act of declaring a kong; 三槓子 is the yaku achieved by having three of them.
From Chinese 三槓子 (sān gàng zi), literally 'three kong pieces'. The reading サンカンツ is a Sino-Japanese on'yomi adaptation.