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1.
'weenis' is the extra skin on your elbow
'butt' is your gluteus maximus, or for you idiots it's the ass
therefore when combined it is the extra skin on someones glutues maximus.
usually used when insulting someone or just complimenting them.
"you're a fuckin buttweenis!" or "wutssup buttweenis?"
by Paloma M. November 19, 2006