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1.
The natural muscular contractions of the inner vagina that, much to the surprise of the provider of pleasure, grabs a hold of the trespasser and pulls it inward.
When I was fingering my girl last night her Box Monster grabbed my fingers and pulled them deeper into the cave. I was flabbergasted!
by theirishpig December 05, 2005
 
2.
Cask of wine. So called because its box shaped, and the morning after consuming one, the box monster jumps around inside your head.
I'm going to the bottle shop, do you want a box monster ?

Ugh, the box monster paid me a visit last night.
by Paul Johnson November 12, 2003
 
3.
woman's camel toe is soooo outrageously huge, she could get a camel toe with a skirt...
Did roast beef curtains fall down, or is that a box monster?
by vegas May 25, 2003