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An abbreviation of the Latin phrase "quod erat demonstrandum". It literally translates as "which was to be demonstrated", and is a formal way of ending a mathematical, logical or physical proof. It's purpose is to alert the reader that the immediately previous statement, which naturally was arrived at by an unbroken chain of logic, was the original statement that we were trying to prove.
"I refuse to prove that I exist," says God, "for proof denies faith, and without faith I am nothing."
"But," say Man, "the Babel fish is a dead giveaway, isn't it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don't. QED."
"Oh dear," says God, "I hadn't thought of that" and promply vanishes in a puff of logic." -- Douglas Adams, from "A Hitchiker's Guide to the Galaxy"


Proof that x + 3 = 0 if x = -3

x + 3 = (-3) + 3
= 0
QED
by redwind64 February 17, 2005
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Nov 27 Word of the Day
A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.
That fucking smooth brain put his shirt on backwards again...

That smooth brain is dumber than a pile of shit.
by Tip Tank May 14, 2011
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2
1) From the Latin 'quod erat demonstrandum', a mathematical term meaning that a proof is complete.

2) A mathematician's way of saying "OH SNAP BITCH!"
"So you see, by this simple proof, your theory is wrong and mine is correct. QED!"
by loudlylikethemouse January 30, 2005
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3
1. Abbreviation of the Latin phrase "quod erat demonstrandum; literally, "that which was to be demonstrated". Commonly used at the end of mathematical proofs to signify the proof is complete.

2. Modern usage expands it to include the conclusion of any proof and is often used in attempts at ironic humor.

3. Quantum electrodynamics.
1. If A=B and B=C then A=C. Q.E.D.

2. Beckham and Ronaldo move to MLS. MLS attracts more fans and makes more money. More money attracts more quality players. More quality players make USA competitive. USA wins World Cup. Q.E.D.

by Alan the Atheist Alphageek April 30, 2008
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5
Originally Latin meaning "quod erat demonstrandum" or "which was to be shown or proven", now used mainly by physics students to insult someone when something is proven wrong or false, typically with the words Mother Fucker added for effect.
Ha! Your wrong.. QED mother fucker!
by ChickensBitch October 27, 2003
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6
Abbr. of quod erat demonstrandum, lit. "which was demonstrated";
cf. res ipse loquitur (the thing speaks for itself), circumstantial evidence, the "smoking gun"
by latlit July 21, 2003
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