Patrol Boat(redirected from Coast defence ship)
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a small warship designed for patrol and guard duty in coastal areas near a country’s own naval bases. Patrol boats appeared during World War I. From the 1930’s to the 1950’s submarine chasers were considered a subclass of patrol boats. Patrol boats have been retained in certain foreign navies. Their displacement ranges from 12 to 90 tons, and they may be capable of speeds up to 45 knots (83 km/hr). They are armed with one or two small-caliber antiaircraft machine guns and depth charges.