to hit someone hard, especially with the flat part of the hand or with something held in the hand

She walloped him across the back of the head. 她在他的后脑勺上猛敲了一下。

to defeat someone easily, especially in sports

"How did your tennis game go last night?" "Oh, I was walloped again." “你昨天晚上的网球比赛进行得怎么样？”“唉，我又输得很惨。”