1 -- A dating relationship that is seen by one as merely a treat, luxury, indulgence or break in one's routine, rather than a stable, steady, routine occurrence. A peoplecake relationship usually involves the parties seeing each other only occasionally or only once or twice a week, with no commitment to exclusivity or building a shared tomorrow. So called because such a relationship is to one's life what cake is to eating: something that's enjoyable but can easily be done without.
2 -- a partner in such a relationship
"Nah, I don't see myself living with Jennifer. What we have is just peoplecake."
"Marilyn, get a grip. Don't go making fantasies about gowns and bridesmaids and china patterns. You have no future with Carlos. To him, you're nothing but peoplecake."