1) An area of land or water that is used or intended to be used for the landing and takeoff of aircraft, and includes its buildings and facilities, if any; 2) Facility used primarily by conventional, fixed-wing aircraft; 3) A facility, either on land or water, where aircraft can take off and land. Usually consists of hard-surfaced landing strips, a control tower, hangars and accommodations for passengers and cargo; 4) A landing area regularly used by aircraft for receiving discharging passengers or cargo.
(14CFR1) (FAA2)