Maximum zero fuel weight

The heaviest weight an aircraft can be loaded to without having any usable fuel in the fuel tanks. Any weight loaded above this value must be in the form of fuel.

Aviation Maintenance Technician Handbook — General, p. G-7

Also defined in 2 more sources

The maximum authorized weight of an aircraft without fuel. This is the total weight for a particular flight minus the fuel. It includes the aircraft and everything that is carried on the flight except the weight of the fuel.

Aircraft Weight and Balance Handbook, p. G-4

The maximum weight, exclusive of usable fuel.

Pilot's Handbook of Aeronautical Knowledge, p. G-19