A misspelling of "tarck bike" which itself is a misspelling of "track bike". A tarck bike is a converted road or track bike to fixed, related to tricks and single gear. "Tark" is slang to describe a bike that poses as a single speed fixed but is not. Coaster brake, internal gear hubs or freewheel would not be tarck. Tark is used commonly to describe a bike or person as a "trendy poser with the soul of a coaster brake".