the backward movement of waves, or the backward movement of water caused by something, such as a boat, passing through it

The waterskier was caught in the backwash from a motorboat. 滑水者遇上了汽艇激起的尾流。

an effect that is not the direct result of something

The economic and political backwash of the war is still being felt. 时至今日人们仍然能感受到战争对经济和政治所造成的影响。