n.1 a a fire or light set up in a high or prominent position as a warning etc. b Brit. (now often in place-names) a hill suitable for this.
2 a visible warning or guiding point or device (e.g. a lighthouse, navigation buoy, etc.).
3 a radio transmitter whose signal helps fix the position of a ship or aircraft.
4 Brit. BELISHA BEACON.
Etymology: OE beacn f. WG