(Brit.)an automatic quick-firing two-pounder cannon of the Second World War period, typically mounted on a ship and used against aircraft (英)（二战时战舰上的）多管高射机关炮
语源
late 19th cent.: imitative of the sound of the discharge
pom-pom
名词 pom-pom:
decoration consisting of a ball of tufted wool or silk; usually worn on a hat