Another slang term for analsex. You basically fuck a girl up the ass so good, and so hard, she"s left feeling like it was just put through a meat grinder.
p.s.
you must have a curved dick for this to be authentic.
Inserting a banana long-ways between your ass cheeks and squeezing as tightly as possible. The only successful banana buttcrunch is one that caused the inner banana to launch out the side of the peel.