Maximum takeoff weight

The heaviest weight an aircraft can have when it starts the takeoff roll. The difference between this weight and the maximum ramp weight would equal the weight of the fuel that would be consumed prior to takeoff.

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

Also defined in 2 more sources

(GAMA) The maximum weight approved for the start of the takeoff run.

Aircraft Weight and Balance Handbook, p. G-3

The maximum allowable weight for takeoff.

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