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!
When you have sex with someone just to cheer them up. Most often in cases of boredom. Comes with no strings attached or emotional investment.
Guy 1: Why did you have sex with Jill?
Guy 2: I was bored and her dog just died.
Guy 1: Oh, so it was a sympathy fuck.
When a girl has sex with a guy because she feels sorry for him. This can be a boyfriend that she is no longer interested in or a guy who follows her around with sad puppy dog eyes.
Girl 1: I had sex with Dylan because I felt sorry for him. I hope he will go away and leave me alone, now.
Girl 2: What? You gave him a Sympathy Fuck? He is going to stalk you now!