(aviation) An obsolescent type of marker beacon, usually used to mark en route airways but occasionally used as part of a non-precision approach, which radiates in a pattern that is considerably wider, from the perspective of an aircraft approaching the marker along the airway, than it is long (allowing an aircraft to pick up the signal from the marker even if slightly to one side of the airway's centerline).

(aviation) A type of VHF radiobeacon which radiates in a tight cone pattern extending vertically from the transmitter; now generally only used to mark specific points along an ILS or IGS approach path, but formerly also commonly used to mark reporting points along en route airways.

plural of air marker

(aviation, historical) A large sign painted on a roof indicating directions and distances to assist pilots in navigating.

plural of marker horizon

(geochronology) A stratigraphic unit of distinctive lithology with a wide geographical extent used in stratigraphic correlation.

(idiomatic) To set the standard.

plural of marker interface pattern

(software, object-oriented programming) A software design pattern in computer science, used with languages that provide run-time type information about objects.

(aviation, chiefly US) A ground-based radio navigation aid consisting of a pair of colocated radio beacons at the final approach fix of an ILS or IGS approach course: an NDB to guide aircraft to the approach fix, and an outer marker to alert aircraft as they pass over the station.