Used in World War II, 'flak' is a German abbreviation for Flugzeugabwehrkanone, or "aircraft defense cannon". 'Flak' was rapidly adopted by the Allies fr obvious reasons.

NOT an abbreviation for "Fliegerabwherekanone".
Flak was quickly adopted by the Allies because in the time it took to say Flugzeugabwehrkanone over the radio, you'd probably already be dead.
by Cataphract_40 October 5, 2004
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Can be used synonymously with "to give someone shit," but in a less profane way. To Nag. Jewish children are often on the receiving end from their mothers.
"The guys gave me flak for my new sweater, they thought it was girly."
by Rafool December 28, 2009
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Flak, from the german "fliegerabwehrkanone", originally referring to land-based anti-aircraft defense systems, has more recently been used when speaking about low velocity shrapnel-based war-time technology (ie the 'flak jacket' etc).

Figuratively, this phrasing is used to allude to broadly targeted aggressive interpersonal behavior.
'he was feeling insecure and start shooting off a bunch flak without realizing she was the one getting hit by most it, what a careless bastard'
by sobieski November 21, 2009
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Anti-air firepower, often seen as black smoke that erupts unexpectedly in midair, although at a certain range (there is a limit as to how far a flak shell can go before exploding in midair, thus allowing a pilot of an aircraft to anticipate flak).
"If you were paradropping, a flak shell will pretty much kill you. If you're lucky, you'll be blinded by the black smoke of the flak. Paradropping is scary in this case, but someone's gotta grow some cojones and do it."
-me
by Dave June 24, 2004
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verb - to hurt or degrade

See also: Flakkin'
I'll flak you up son!
by Baruchhhh February 7, 2007
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