An aquatic bird that, in medieval times, was used to find out if a person was a witch or not.

This stems from the very logical idea that if a person weighs the same as a duck, then that person is made of wood (because both ducks and wood float in water). And since wood burns (just like witches) then that person must be a witch, because witches are made of wood.

Therefore, the accused person(s) would be placed on a scale next to a duck, and if they balanced, the person(s) would be burned.
So, if she weighs the same as a duck, then she's made of wood. And therefore... A WITCH!
by Flint October 27, 2003
We found a witch! May we burn her?
A witch? How do you know she's a witch?
She turned me into a newt!
A newt..?
I got better..
There is a simple way to figure out if she is a witch or not.
Witches burn, and what else burns?
Wood!
Yes, and wood floats. What else floats?
... A duck?
Yes! So if this woman weighs as much as a duck, than she is a witch!
by WhiteyLights July 15, 2005
What floats on water and weighs the same as a witch.
When asked by Sir Benomir, what also floats, King Authur exclaimed "A duck".
by Cosmicstargoat January 30, 2004
An insurance salesperson who is continually frustrated by humans who refuse to listen.
by Cosmicstargoat June 5, 2004
What looks like a duck, swims like a duck, and quacks like a duck, is a duck (probably).
Where duck is used as a metaphor for something usually totally unrelated to ducks.
"Hey, is that guy a republican?"
"Well, if it looks like a duck, swims like a duck, and quacks like a duck, it's probably a duck."
by gothfae May 2, 2004
toya, you are such a duck, you believe that i am out of town
by jakeema November 3, 2003
In the sport of cricket, when a batsman is out without scoring any runs (points).

Also:
Golden Duck - when a batsman is out after only facing one ball

Royal Duck - when a batsman is dismissed by the first ball of the innings
"I didn't score any runs, I got a duck"
by Corps October 16, 2004