1) Air-defense fire 2) Air-raid gun 3) Anti-aircraft fire 4) Antiair-craft fire 5) Antiaircraft gun 6) Gun aimed at a bomber 7) Kind of gun 8) Sound of gunfire 9) WWII gun Found on https://www.crosswordclues.com/clue/ack-ack
[horse] Ack Ack (February 24, 1966 - November 7, 1990) was an American Thoroughbred Hall of Fame racehorse. He raced with success at age two to four, scoring wins in the important 1969 Withers Stakes and Arlington Classic. In 1971 at age five, Ack Ack blossomed into the year`s most dominant horse. Conditioned by Charlie Whittingham, he won ... Found on http://en.wikipedia.org/wiki/Ack_Ack_(horse)