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2.
A threesome with one girl and two guys.
"Yo, what's a treesome?"
"It's just like a threesome, but with more wood"
by JGreenFruit July 26, 2013
 
1.
When two people have sex up a tree. Yes, the tree is like and extra person there alot you and do with it ... use your imagination!
Derek: Let's have sex
Ronnie: Ok
Derek: Just you, me and the tree
Ronnie: Ohhhh, a treesome you thoughtful bastard
Treebranch: Ohhhhh baby ...
by PrezMeister December 06, 2007
 
3.
A threesome or threeway where two (or all three) of the members are in the same family tree.
Becky is such a slut, she had a treesome with the Dailey cousins.
by Alek K. August 27, 2008
 
4.
A threesome or threeway where two (or all three) members of the orgy are related (part of the same family tree).
Becca had a treesome with the Bailey cousins.
by Nutwrap September 05, 2008