The same as the difference between vagina and pussy: time and audience. The first is a bit " Fuck buddies " are two people who agree to get together for the sole purpose of sex. They do not hang out or talk unless sex is on the line and hence. The sex with Lisa is great but she's a pain in the ass - I wish we could just be fuck buddies and not boyfriend/girlfriend. by greekmonkey April 08. What exactly defines a fuck buddy? I'd call it someone that you only ever see with the intention of sleeping with. You don't hang out outside of Fuck buddy?.