To have a casual sexual relationship with someone. Betsy and I are just fooling around, which is great because I don't want a serious relationship anyway.

Is fooling around an idiom?

to waste time doing something unnecessary or doing something amateurishly. ... I wish you didn't spend so much time fooling around.

What does it mean to be fooled by someone?

fooled. DEFINITIONS1. to trick someone by making them believe something that is not true. I was completely fooled by her.