A condition of heightened anxiety and short temperedness brought on by a combination of frustration, long-drive induced claustrophobia, fatigue and lack of cold beer. Dubbed after a nickname of Winnipeg, Manitoba where the condition was first formally documented.
Actual Transcript of initial case of the Peg, summer 2006:

Index Case(IC): "Winnipeg sucks!"

Innocent bystanders (IB): "Oh man Jenny is getting the Peg, we gotta pull over and get some beer into her."

IC:"How dare you accuse me of getting Peggish!"

IB: "Easy now, don't Peg out...look, see? A Boston Pizza, they have a patio and beer. Pull over."
by Dudebun December 5, 2007
To have figured a person out
"You've got me so Pegged"
by MonzParadox January 15, 2007
to run away very quickly. see also leg it
someone was running at me so i pegged it.
by DTR February 6, 2004
A man who receives anal from a woman with a strap-on
by Hejernebehe June 2, 2018
To falsely assume something about a person. Often based on stereotypes or outward appearances. It can be used in both the positive and the negative (ie, someone is "pegged" with a characteristic they do not possess; or they are "not pegged" with a true but hidden characteristic.)

Derived from the hypothetical idea of "pinning (or pegging) a label on someone".
"I never would have pegged Ben for a geek, but then I discovered his collection of Star-Wars action figures."

"I'm sick of people pegging me for a homosexual. There's nothing wrong with a little judicious manscaping here and there!"
by Violet Clementine September 14, 2008
Meaning to 'leg it' or to go somewhere on foot.
by Nathan January 17, 2005
Being struck with an object which someone else threw at you, such as a tennis ball, dodge ball, football, crumpled up piece of paper.
Dude, Jack was walking to his car and I pegged him with a tennis ball in the back of the head.
by andrew82 January 18, 2008