A person, usually a nerd, who keeps his piss in a jar in his freezer and sells it to althelets when drug testing comes along. Wiz tenders generally have never gotten a buzz in their life.
Stoner: Shit man, I have to get tested today. I got wasted a few hours ago!
Resourceful Stoner Friend: Why not just go to the wiz-tender. He'll selling for $10 a cup.
Stoner: Great idea! Thank you my resourceful stoner friend!
Resourceful Stoner Friend: Anytime.