(n.) A tower or other building with a powerful light at top, erected at the entrance of a port, or at some important point on a coast, to serve as a guide to mariners at night; a pharos.

Klaxon Mayday SOS Texas tower air-raid alarm alarm alarm bell alarm clock alarm signal alarum alert all clear antenna tower barbican beacon belfry bell tower belvedere bench mark bleachers blinking light bookmark bridge burglar alarm buzzer cairn campanile catstone colossus column conning tower crostarie cupola derrick direction dome fiery cross fire alarm fire bell fire flag fire tower five-minute gun flashing light fog bell fog signal foghorn gale warning gallery gazebo grandstand guidance hooter horn hue and cry hurricane warning landmark lantern lightship lookout loophole mark marker martello martello tower mast menhir milepost milestone minaret monument note of alarm obelisk observation post observation tower observatory occulting light outlook overlook pagoda peanut gallery peephole pharos pilaster pillar pinnacle platform pole police whistle pylon pyramid ringside ringside seat seamark shaft sighthole signal of distress siren skyscraper small-craft warning spire standpipe steeple still alarm storm cone storm flag storm warning stupa television mast tocsin top gallery tope tour tower turret two-minute gun upside-down flag watchtower water tower whistle windmill tower