talk one's head off
Fig. Inf. to talk endlessly; to argue vigorously. I talked my head off trying to convince them. Don't waste time talking your head off to them.
talk someone's head off
1. Fig. [for someone] to speak too much. Why does John always talk his head off? Doesn't he know he bores people? She talks her head off and doesn't seem to know what she's saying.
2. Fig. to talk to and bore someone. John is very friendly, but watch out or he'll talk your head off. My uncle always talked my head off whenever I went to visit him.