Having sexual intercourse with and ejaculating into any raw cut of meat (e.g. liver, porterhouse steak, pork roast), and then preparing and serving said meat (colloq. 'marinated') as a meal for one's immediate family or close friends.
(Origin: Portnoy's Complaint, by Philip Roth)
I was horrified when Andrew told me he'd done the Portnoy on the steak tartare I'd just enjoyed so heartily.