(Canadian usage)
1)To be verbally insolent, belligerent or insubordinate;
2)To be mouthy to or backtalk someone;
3)To complain profusely about something.
"I'd love to dig a new trench, Sergeant. And if I thought you knew what you were talking about, I might do it."
"Are you beaking off, Corporal?"
"He's still beaking off about losing the election, and that was six months ago!"
Running your mouth or playing around.
Tyler is beaking off over there. Someone please tell him to put that beak away.