Antiaircraft artillery is a type of military weapon used to defend against aerial attacks. The term can be broken down into four crossword solutions: FLAK (4 letters), ACK (3 letters), SAMS (4 letters), and NIKE (4 letters). FLAK stands for 'Flugabwehrkanone, ' which is German for 'anti-aircraft gun.' ACK stands for 'Anti-Aircraft Command, ' which is a branch of the United States Air Force. SAMS stands for 'Surface-to-Air Missile System, ' which is a type of missile defense system. Finally, NIKE stands for 'National Interception and Keep Engaged, ' which is a type of air defense system developed by the United States Army.