Streaming a nut in her box
The act of ejaculating (e.g. 'nutting', usually sans condom) in a chicks vagina (e.g. 'box').
"Dude, what happened with that hottie last nite?"
"Well, I was streaming a nut in her box when the doorbell rang."
"Well, I was streaming a nut in her box when the doorbell rang."