A metal plate which restricts something; specifically one which limits the air intake of an internal-combustion engine, chiefly used in motor racing for reducing the maximum speed of a car.
Origin
1930s.
Definition of restrictor plate in US English:
restrictor plate
noun
Engineering
A metal plate which restricts something; specifically one which limits the air intake of an internal-combustion engine, chiefly used in motor racing for reducing the maximum speed of a car.