越雷池一步 - Chinese Idiom

越雷池一步:

Literally means:

transgress the bounds; cross the line

Actually means:

越, means transgress; 雷池 is a place in the south of Wangjiang County of Anhui Province. Literally, the phrase means transgressing Leichi to attack another place. Metaphorically, it means going beyond some limit or bound.

越，超出、超过；雷池，今安徽望江县南，意为越过雷池去攻打别的地方。比喻做事超越一定的界限、范围。