Foreign object damage (FOD)

Any damage caused by any loose object to aircraft, personnel, or equipment. These loose objects can be anything from broken runway concrete to shop towels and safety wire.

Aviation Maintenance Technician Handbook — General, p. G-5

Also defined in 1 more source

Damage to a gas turbine engine caused by some object being sucked into the engine while it is running. Debris from runways or taxiways can cause foreign object damage during ground operations, and the ingestion of ice and birds can cause FOD in flight.

Pilot's Handbook of Aeronautical Knowledge, p. G-12

Taught in PP-B Concepts, GEN-F Quick reference, GEN-F Procedures, PP-B Quick reference, GEN-F Concepts, PP-B Procedures and 3 more.