a sexual experience/position involving four parties usually 2 males and 2 females. One male lays flat on the ground with an erect penis. the two females then proceed to mount on the mouth and penis. the second male then stands over over the first male in between the two female, whom are facing each other, and receives oral stimulation from both females, orally and anally.
Bob: Hey David! I have two female companions wishing to engage in a quadrilateral.

David: Oh bro I call top!

Bob: Oh darn, I desired a good salad tossing
by quadpro September 20, 2010
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a thing that slowly collapses on itself, destroying the universe
can only be made in a math class
Person drew an quadrilateral triangle. Everyone is now dead and the universe has been destroyed.
by Rexcanyon792 December 5, 2018
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Created in 2021, the Vaccarella Theorem of Quadrilaterals places an emphasis on the vagueness which can be applied to everyday examples. A rectangle, in terms of quadrilaterals, is a specific parallelogram in which each pair of adjacent sides is perpendicular. On the contrary, squares are regular quadrilaterals that have four equal sides, along with four right angles. Using this information, one can identify that squares have more specific conditions than rectangles. Moreover, all squares are rectangles, but not all rectangles are squares. This means that squares can be viewed as the less vague topic in any situation, due to them being less likely to occur in the world of quadrilaterals. On the other hand, Rectangles can be seen as the more vague topic, due to them requiring less conditions to exist. One could use this when analyzing any given situation. For example, if one was to look at the issue of poverty within the United States, the Vaccarella Theorem of Quadrilaterals could be applied by saying that the general issue of poverty is the rectangle, whereas the issue of homelessness could be seen as the square. The Vaccarella Theorem of Quadrilaterals goes further than just rectangles and squares, and if needed, one can apply even more quadrilaterals to further differentiate parts of a situation, by simply increasing the complexity of quadrilaterals and adding them to the comparison.
"That was a crazy game, too bad the defense played so bad. I was just thinking about the Vaccarella Theorem of Quadrilaterals. The whole team was pretty bad today actually, it's like the team as a whole was the rectangle, but that one turnover in the fourth quarter was definitely the square."
by Beetlejesus November 9, 2021
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A term for a group sex position formed when four guys penetrate a girl at precise angles.

The term is commonly used by millennials and leaves Randy in a state of confusion and distress.
Gene: "Yeah, man. That's when you hit her with the quadrilateral!"

Randy: Quadrilateral??? What is that???"

Joe: "Hell Yeah! The quadrilateral! Works everytime!"

Randy (Losing his mind): "Quadrilateral??? What the fuck are you guys talking about!!??"
by Jkru94 April 1, 2019
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