Gay buddy that meets you on occation to "fuck" and also happens to be your best friend. (man on man only)
Hey did you know that steve, joes best friend is a "Butt Brother" and they fuck on occation. (
by scott pitts February 16, 2005
The connection two men gain after they share a common toilet seat. Similar to Blood brothers, but hopefully, no blood is involved.
After Jason took a dump in our shared bathroom at work we became "Butt Brothers."
by foureyedg November 16, 2009