fool around ( also fool about British English ) phrasal verb ( see also ↑ fool )
1 . to waste time behaving in a silly way or doing things that are not important SYN mess around :
He always used to fool around in class.
2 . to behave in a way which is careless and not responsible SYN mess around
fool around with
Some idiot’s been fooling around with the electricity supply!
3 . American English to spend time doing something that you enjoy, but that does not have a particular purpose SYN mess around :
The boys were out in the yard, just fooling around.
4 . to have a sexual relationship with someone else’s wife, boyfriend etc SYN mess around :
She found out that he’d been fooling around behind her back.