Extension of baines, used to describe someone who achieves something legitimate.
Guy 1: "Did you hear about Sam?"
Guy 2: "No, what's he done this time?"
Guy 1: "He only went and hit the gym early this morning, smashed out a 130kg bench and then hit the libes for 6 hours to get some savage work done before tonight."
Guy 2: "Fuck me, that guy is such a bainer!"