Quite simply, having sex with another man's balls; similar to tit-fucking, a banana split is achieved when a man wraps another man's testicles around the shaft of his penis.
I couldn't fuck my best friend's father: he only had one testicle, and I just love to Banana split.
When you fucking a girl on her period, make a bloody mess, pull out, start titty fuckiner her, cum in her face, and then shit on here stomach creating a banana split.
It took me a couple seconds to shit on her but I made my bananasplit.