originally, a Vickers-Maxim one-pounder automatic machine cannon using metallic ammunition fed from a lopped belt attached to the gun; -- popularly so called from its peculiar drumming sound in action. More recently, the term is applied mostly to automatic antiaircraft cannons.

One-pounder automatic Maxim gun with 25 shells on a belt

a large calibre machine-gun, used mostly famously as an anti-aircraft gun by the British Royal Navy

artillery designed to shoot upward at airplanes

decoration consisting of a ball of tufted wool or silk; usually worn on a hat