fool around with
idiomDefinition of fool around with
1
: to use or do (something) in a way that is not very serious
I'm not really a painter; I just like to fool around with paints.
2
: to handle or play with (something) in a careless or foolish way
Don't fool around with that gun.
3
: to have sex with (someone who is not one's husband, wife, or regular partner)
His wife discovered that he was fooling around with his secretary.