PT boat /ˌpiː ˈtiː bəʊt/ BrE AmE noun
a small, fast boat used by the US military forces, especially during World War II. It was used especially for firing ↑ torpedo es (=explosive weapons that travel under the sea) at enemy ships. Many Americans remember that President John F. ↑ Kennedy fought during World War II in a PT boat, called PT 109, and that when it was sunk, Kennedy led the men to safety.