the Coast Guard a military organization in the US that is in charge of watching for ships in danger and preventing illegal activities in the ocean. Naval force that polices compliance with a nation's maritime laws and assists vessels wrecked or in distress on or near its coasts. First established in the early 19th century to discourage smuggling, coast guards may maintain lighthouses, buoys, and other navigational aids and provide emergency aid to merchant sailors and to victims of natural disasters. Duties may include icebreaking in inland waterways and the collection and broadcasting of meteorological data concerning floods and storms. In several European countries, volunteer lifeboat associations handle coast-guard duties