Artificial intelligent assistant

ack-ack

ack-ack, a. and n.
  (ˈækˈæk)
  Also Ack-Ack.
  [Redupl. form of ack, repr. A.A. (see A III).]
  A. adj. Anti-aircraft. B. n. Anti-aircraft gun, gunfire, regiment, etc.

1939 Collier's 2 Dec. 19/1 One unscheduled move and the machine would have been blown from the air by those long, lean guns the British call Aak Aaks, signalers' code for anti-aircraft. 1940 R. Walker Flight to Victory vii. 49 Engine failure due to ack-ack fire. 1943 E. Bone tr. W. Wassilewska's Rainbow vi. 105 ‘There are more guns under the limes...’ ‘Ack-ack perhaps?’ 1944 Amer. Speech XIX. 293 Some fliers who, in their conversation, were careful to distinguish between the enemy's flak and our ack-ack. 1944 ‘N. Drew’ Amat. Sailor ix. 267 Occasionally, for extra special shows, an ack-ack cruiser was in attendance. 1945 Daily Express 20 Apr. 4/6 Captain Flack A.A.—Captain Flack, of the Ack-Ack, has been transferred to the Royal Engineers.

Oxford English Dictionary

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