|2.||busting one's balls|
To bust one's balls is to mess or joke with someone.
Person 1: I slept with your girlfriend last night.
Person 2: Are you serious?! I'm going to kill you!!
Person 1: I'm just busting your balls! I would never sleep with your girlfriend.
|1.||busting one's balls|
"balls" is refering to someone's ego
so busting someone's balls would be making them insecure in some way
busting one's balls could be messing with them, annoying them, teasing them, embarrasing them, etc.
they use this phrase a lot in the movie "The Goodfellas"