hang out/knock around 表示闲逛的区别.

hang out
（非正） (呆在某处，或与某人呆在一起)闲逛，出去玩儿
why do you just hang out in bars?Do you want to hang out with me instead
你只呆在酒吧玩吗？何不跟我一起去玩？
knock around
漫游; 四处走动
I've knocked around in most parts of the world in my time.
我这辈子差不多游遍了整个世界。
He has knocked around quite a bit.
他经历过很多漂泊不定的生活。
He's not yet thirty, but he's knocked around the world a good deal.
他还不到30岁, 但他已漫游了世界许多地方。

hang out悠荡,闲逛Where were you hanging out these days?
knock around 在...流浪,在...无目的地旅行(不可用被动语态)