Notice To Air Missions (NOTAM)

Formerly "Notice To Airmen"

A notice containing information (not known sufficiently in advance to publicize by other means) concerning the establishment, condition, or change in any component (facility, service, or procedure of, or hazard in the National Airspace System) the timely knowledge of which is essential to personnel concerned with flight operations.

Source: Pilot Contoller Glossary (PCG)