Seat at a poker table from which statistically unlikely bets/calls succeed at an unlikely rate. See also: Jammy Get, Spawny Bastard.
Suggestive or indicative of unnatural luck: a wan seat.
Player1: "You just called my trip aces with an inside straight draw with one card to come and completed your straight on the river to knock me out and win £1000."
Player2: "Why of course. I am sat in the Wan Seat. What else did you expect to happen?"