contact
Aviation term: a verbal queue expressed by the pilot of a propeller-driven aircraft lacking a starter to a mechanic positioned forward of the engine, indicating that the pilot has connected the main electrical circuit of the aircraft via a switch in the cockpit, and that the mechanic should manually rotate the propeller in order to start the engine.
Example:
"When Lt. Rickenbacker engaged the main switch of his S.P.A.D. fighter, he shouted 'Contact!' to his mechanic to crank the propeller."
"When Lt. Rickenbacker engaged the main switch of his S.P.A.D. fighter, he shouted 'Contact!' to his mechanic to crank the propeller."