This document defines and explains 6 common trucking terms: bobtailing refers to driving a semi-truck without a trailer; deadheading is driving a semi-truck pulling an empty trailer; a reefer is a refrigerated trailer used to transport perishable goods; the cab is the driver's compartment of a truck; GVWR is the maximum allowable weight for a vehicle; and a Jake brake is an engine braking system used to supplement wheel brakes on semi-trucks.