The act of having sex with someone as a consoling gesture, immediately after breaking up with them.
The true purpose is to allow you a safe window of opportunity for collecting your property from their house.
(This generally occurs within an hour or two of the breakup, but it can sometimes qualify as a sympathy-fuck even a few days later if circumstances are extremely bad)
After I dumped that bitch she went psycho. I had to throw a sympathy-fuck on her just to get away with my CD's and my coat!