shadow factory

plural shadow factories

1. UKhistoricalAn aircraft factory in the World War II era, partly staffed by people from the motor industry, that was kept hidden from enemy aircraft.

   [...] but common prudence demanded, even before the outbreak of war, that details should not be disclosed which might reveal to a potential enemy the positions of "shadow factories" and air bases, and the location of stores of munitions, petrol, food, and so forth.

   1939 November, Charles E. Lee, “Railways and the War — I”, in Railway Magazine, page 313