(n.) The center position on a three cushion couch typically occupied by a neophyte pot smoker who by virtue of his location is offered two tokes off a joint or a pipe for every one of his compatriots. Since the "guru" is usually too inexperienced to refuse a hit, he gets much more stoned than his friends resulting in endless fun at the "guru's" expense.
Friend 1: You're in the guru seat, so you gotta take a hit every time the joint comes your way.
Guru: Cool. You guys are awesome.
Friend 2: No, man. You're awesome. Now take another hit, bitch. Guru seat rules apply.