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1.
LSD, a 'hit' of 'acid'
A small square of dried translucent substance containing a ‘hit’ of acid, that is, LSD, and resembling a ‘gel’ used in theatrical lighting. It dissolves in liquid, melts in your mouth.

A form of acid from the 70s. It came in colors (pun intended) such as amber and brown. Hence the name Amber Windowpane.
I took a hit of Amber Windowpane about an hour ago--man your face looks weird.
by LoganC October 13, 2006
 
2.
In a similar way to the game of Safety/Doorknob for farts, then Window Pane is called when a friend burps within earshot. You are then entitled to punch them until they touch a window pane.
In order to protect oneself from being punched, you can call Security or just say a simple "Excuse Me".

Other derivatives of Safety/Doorknob include Tent Zipper, and numerous others I can't think of right now that are more appropriate to a particular situation.
Josh: (Burrrrrp)
Spencer: Window Pane!
Josh: Crap...
(Spencer beats the crap out of Josh, until Josh stands up - especially amusing in class - and touches a window pane)
by verk August 21, 2006