The morning when zombies will rise from the dead and feast on the flesh of the living...
Kirk: Hear ye, hear ye, Z day appoaches... Repent sinners...

Sinners: Eh, eh, rick my barrs...

Kirk: Well, fuck off you salad tossers, me and my party are all meeting at Jordans...
by Buphstuph17x November 3, 2005
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This term was used by the British Expeditonary Force in preparing for the Battle of the Somme in 1916. It culminated previous days of artillery bombardment called U,V,W,X,Y days. The actual time of attack was called Zero-Hour. Compare these with D-Day and H-Hour used by American troops late in that conflict, terms which became more widespread during WWII.
"Z Day" is found in numerous historical accounts from the time. For instance, from Guy Chapman's wartime memoir, "A Passionate Prodigality": "We were waiting for Z day. ... Once more Z day was postponed."
by New Nutmegger August 18, 2011
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Noun (zee day): A term probably coined by Max Brooks which refers to the war between zombies and mankind. Derived from the word D-Day, which is a British term used to refer to a variable day on which a combat attack or operation is initiated. Z-Day is marked by a sudden attack on mankind by zombies, which will lead to a widespread zombie outbreak. There are a number of zombie survivalist groups worldwide (largely in the US, UK, and Canada), that are already planning what to do when this day comes.
Z-Day will catch mankind completely off guard, and the lack of preparation will lead to countless casualties.
by Edward Stevens August 25, 2006
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The day when zombies are said to rise from the grave due to radiation,a virus ,or something else, and generally cause chaos .While most people don't beleive that this will ever happen , There are millions of web pages soley dedicated to helping people be ready for z-day.
Some people even have a z-day survival plan and treat it as seriosly as you would treat a survival plan for if there was nuclear war.
Matt : Hey Joe , do you have a plan for Z-Day ?

Joe : what's that ?

Matt : It's when the dead are gonna rise from the graves and become zombies , and there will be chaos and everyone will go crazy

Joe : okay ...I think you've allready gone crazy
by Victoria Violet October 21, 2006
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Calling off work every Monday with a stupid excuse
Awe dude!!! i'm taking a z day today cuz i got explosive diarrhea

you ok? what happened?

My mama made some cookies last night and it tore up ma stomach boiii
by ezdoesit2me September 6, 2008
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Calling off work every Monday with a stupid excuse
Awe dude!!! i'm taking a z day today cuz i got explosive diarrhea

you ok? what happened?

My mama made some cookies last night and it tore up ma stomach boiii
by ezdoesit2me September 24, 2008
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any day that one takes to avoid daily responsibilities(usually a day of school)by faking some kind of illness.
"Man, i heard she's taken like 20 Z-days already this year"
by T-lzr April 7, 2009
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