First letters interchanged of "stupid cunt." While the phenomenon of accidentally interchanging the first letters of adjoining words is not uncommon, use of cupid stunt is generally intentional and merely a way of euphemizing or masking an extremely offensive epithet.

It's a great, PG-13 way to call someone a Stupid Cunt.

A Cupid Stunt is a retch of a person. Originating in Florida's prison system, the term is spreading through the southwest US states. A Cupid Stunt can be a Paedophile, rapist or generally any sexual predator.