An inside joke between people who are not overweight or obese: a term used to indicate that a person is obese without them knowing what you're talking about. The term alludes to the person looking like Old Saint Nick (aka Santa Clause), but uses "Dr." as a substitute for "Saint" so as to disguise the meaning from the person considered obese
When my wife asked me if I thought she was fat, I knew the only way I could tell her the truth without spending the next week on the couch was to reply, "HiDrNick!"
Whenever the subject of my weight comes up with my parents, they both just say "HiDrNick" and laugh together for some reason.
Chester : Dude, check out my new physique? Aren't I ripped!
Devon: HiDrNick, you certainly are ripped.
(fat) Isaac: What? Where? Why?
(skinny) Kenny: Ohhhh! hahahaahahahahahaha!