mop up 的up是什么词

up是副词.
mop up 做扫尾工作；擦,抹；痛击；吃完
如：
1.Please mop up the mess .
请擦掉这堆脏东西.
2.Two companies were left to mop up.
留下两个连进行扫荡.
3.We must mop up the arrears of work .
我们必须把耽误的工作做完.
4.You should have seen him mop up his dinner.
他该看看他那狼吞虎咽的样子才好.