A White Buffalo is when you exhale an exuberantly white, very thick plume of smoke that resembles a very awesome dense cloud.
Dude1: (blows out a super thick plume of smoke after hitting the hotrail tube/pipe)
Dude2: Whoa bro!! White Buffalooooo!
Dude1: Wwwhiiitteee Buffaalloooo (while exhaling all that smoke)
Dude3: You are a master at blowing out those White Buffalos!!!