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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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."
by Dave June 24, 2004
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Flak is slang for any type of jacket. This can be a hooded or unhooded but it must be a jacket, it does not refer to jumpers.
James:Blud its cold out init
Me:Good observation my friend could you pass me my flak then to conserve my warmth?
James:Wagwan cool yeh safe one wun up here you go
by The Ville May 28, 2007
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the proccess of using a male or female's pubic hairs to floss one's teeth
Rob had some gunk in his teeth late at night so instead of walking to the bathroom he just flakked with Ingrid.
by PussicusS February 22, 2012
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Hot, tall drink of water of Australian origin. Has a decided preference for brunettes. Follows directions moderately well.
Flak is sooo sexy. Where's my bottle of brown hair dye?
by Jules March 25, 2005
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