to prevent a bomb from exploding

Bomb disposal experts have defused a 110-pound bomb at a subway station this afternoon. 今天下午，排弹专家在一个地铁站拆除了一枚110磅的炸弹。

to make a difficult or dangerous situation calmer by reducing or removing its cause

The two groups will meet next week to try to defuse the crisis/situation/tension. 双方将于下周会面以求缓和危机／局面／紧张局势。