'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?"
Its that gross shwag that has spider webs in it and shit. It smells bad, not even like weed something more like dirt and its usually also in a shitty bag. You can smoke mad blunts and wont even get high. Its is rumored to actually be shipped out of illegal mexican butts.
Eww dog fuck this "mexican buttweed". Ive smoke 3 blunts of this mexican buttweed and still not high.