From Longman Dictionary of Contemporary Englishfool around (also fool about British English) phrasal verb1 STUPID/NOT SENSIBLEto 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 STUPID/NOT SENSIBLEto behave in a way which is careless and not responsible SYN mess 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 SYto 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. → fool→ See Verb table
Examples from the Corpus
fool with• This seems like a guy I can fool around with.• I fooled around with a lamb chop for a while, but decided I wasn't really very hungry after all.• Why fool around with money, or taking teeth out, when I might not enjoy it as much?• I make a policy of never fooling around with my clients.• Matt thinks his wife is fooling around with someone.• Augie and I are fooling around with them.• Stop fooling around with those scissors before you hurt yourself! 