A sex position in which the woman lies down on a flat object, like a bed or a table, and her legs are on the man's shoulders, and the man's dick is in her asshole.
Man 1: I broke up with Sherry yesterday.
Man 2: Good. because last night I took her home and she begged me to go butterfly position with her.
Man 1: Fuck you.
(A large fight then ensues.)