1917, in the meaning defined above
British signalmen's telephone pronunciation of AA, abbreviation of antiaircraft entry 1
Time Traveler for ack-ack
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Cite this Entry
“Ack-ack.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ack-ack. Accessed 27 Nov. 2021.
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