A fluffer is someone employed on the set of a pornographic film with the purpose of keeping the actors penises aroused and ready for when the cameras roll. They may do this physically via oral or manual stimulation or in a way that does not involve touching the actor at all.
There is some debate as to whether the existence of fluffers is real or simply an urban legend of the adult film industry. Several adult film stars have spoken out to say that there is no such job on set. The continued belief in the myth of the fluffer could be traced to society's willingness to believe that pornography reflects a world where there is constant sexual activity; and the fluffer would be just another part of that.
