To play with ones balls or to play with someone else's balls. To diddle with someone's balls.
Can also be used to so others think you did something cool when really you were home alone playing with your balls.
co-worker 1: What did you do last night?
Co-worker 2: I was ballin'. (looking at porn)
Co-worker 1: (I wish I was as cool as co-corker 2)
2👍 5👎