A usually legitimate grievance against a particular person. The offending person either is unaware of the grievance or has been studiously avoiding acknowledging it - usually the latter - and will probably never acknowledge that this is a real, legitimate complaint.
I've got a bone to pick with you. You really violated my personal boundaries yesterday, and that wasn't cool.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.