when you put whip cream in a girl's mouth and pussy or ass, and you stick a banana in the girls pussy or ass, then 2 other people eat from the tip of the banana to the end.
when a man performs a reverse deep stick sexual position on his partner (either in the pussy or asshole) while the partner eats out his asshole and/or sucks on his ball sack.
matt: hey girl you wanna get banana splitted?
girl: hell no! the last time i did that i had the taste of ass in my mouth and my pussy hurt for weeks
When a transgender male to female has the full vaginoplasty, the penis is split in half and pushed back inside creating a fully functional and cosmetically accurate vagina. Slang for the operation is the banana split.