A large bucket from which one consumes large quantities of alcohol within a short period then vomits back into it. This process is often repeated with fresh beer with or without rinsing a number of times in one night.
Eric: Did you see that girl at Bill's party the other night? She chugged a tonne of beer in like ten minutes!
Harry: Oh yeah, she was doing a chugbucket.
Harry: Yeah, she did it about five times, it was sick!