1) Alarm 2) Alarum 3) Alert 4) Bank alarm 5) Big bellowing voice 6) Blast from a lighthouse 7) Fogsignal 8) Harbor sound 9) Loud seaside signal 10) Sound at sea 11) Two-note instrument 12) Warning from a bank 13) Warning signal 1) Alarm 2) Diaphone 3) Fog signal 
A foghorn is a fog signal that uses sound to warn vehicles of navigational hazards or boats of the presence of other vessels in foggy conditions. The term is most often used in relation to marine transport. When visual navigation aids such as lighthouses are obscured, foghorns provide an audible warning of rocks, shoals, headlands, or other danger...
Foghorn is British slang for someone who talks loudly.
[n] - a loud low warning signal that can be heard by fog-bound ships 2. [n] - a warning device consisting of a horn that generates a loud low tone
fogsignal noun a loud low warning signal that can be heard by fogbound ships
a deep, loud horn for sounding warning signals in foggy weather, as to ships. · a deep, loud voice.