The middle line separating the two halves on a Chinese chessboard (Xiangqi).

象棋棋盘的中间刻有“楚河汉界”四个大字。

A line or boundary that separates two rival territories, factions, or opposing sides.

在这次利益分配中，两家公司之间划清了楚河汉界。

The literal river and border that divided the states of Chu and Han during their historical conflict.

历史上的楚河汉界就在今天的河南境内。