from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Slang An antiaircraft gun.
- n. Slang Antiaircraft fire.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Antiaircraft artillery.
- n. Antiaircraft fire
- adj. Of or relating to antiaircraft warfare.
from the GNU version of the Collaborative International Dictionary of English
- n. Artillery designed to shoot upward at airplanes; antiaircraft artillery.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. artillery designed to shoot upward at airplanes
British telephone code for AA, abbreviation for antiaircraft.(American Heritage® Dictionary of the English Language, Fourth Edition)
From ack ("A") + ack ("A"), RAF WWI signalese for AA ("anti-aircraft"). (In modern signalese it would be called alpha-alpha.) (Wiktionary)