The act of taking a shit and smoking a bowl at the same time. Reported to be twice as relaxing (taking a dump is a very relaxing experience) and smoking a bowl (which is super chill).
If you don't know how to chill, though, you get a swirly.
Mark: "hey bro you wanna hang at the party? I heard Stef and Amanda are gonna be there"
Jo: "Sounds good bro, just doing a Dean then gonna have a chat with the bathmat"