Slang: synonomous with asshole. Mainly because a normal tight sphincter resembles the inside of a knot made on a baloon.
Hey ... last night I popped her right in the baloon knot.
by Joey Provalone January 24, 2003
Noun: slang for anus. Just look at an inside out baloon and you will understand.
My dog must have worms because he is dragging his baloon knot across the floor!
by EugeneGoldman October 25, 2007