Airburst round
An airburst round is a type of tactical anti-personnel and anti-aircraft explosive ammunition, typically a shell or grenade, that detonates in midair, causing air burst effect fragment damage to enemy personnel or aircraft (notably comparably unsophisticated unmanned aircraft systems such as modified racing drones). In the latter case, airburst rounds are used in anti-aircraft or "zenith" cannon, known in military slang as FLAK (from the German "fliegerabwehrkanone", air defence cannon) or ack-ack (from the British phonetic alphabet, as an initialism for Anti Air).