The act of breaking up with your significant other through the offering of poo cake. Essentially, the slighted party bakes an extravagant cake for their partner, takes a dump on top and then leaves it for them as a gift. Often, a goodbye message such as, "Piss off, asshole", will be written in red icing as well.
Bill: "Hey Brad, did you break up with Suzie after you caught her cheating on you?"
Brad: "Yes. I left her a lovely defecake on her dorm room table earlier today. Hope the whore and her roommates enjoy it."