fool around主要有两个解释：

　　1. 闲荡；游手好闲；干无用的事 to waste time instead of doing something that you should be doing

　　例句：

　　The workers always fool around when the supervisor steps out.

　　当工头一走开，工人就到处游荡。

　　下面给出两个句子，大家可以尝试翻译一下：

　　It was a serious academic school, not a place to fool around.

　　Stop fooling around and clean your room as I told you.

　　2. （和某人）乱搞（男女关系）；胡搞；婚外情 to have a sexual relationship with another person's partner; to have a sexual relationship with somebody who is not your partner

　　例句：

　　All hell broke loose when his wife discovered he was fooling around with another woman.

　　当他太太发现他跟别的女人胡搞时,情况变成一团混乱。

　　下面给出一个句子，大家可以尝试翻译一下：

　　If someone fools around with another person, especially when one of them is married, they have a casual sexual relationship.