A person(usually a female)that is used only for sex.
In the fetish community fuck toys are consensual creatures that are submissive (bottom) to a master or a mistress (the top). The toy submits to guidance and sexual exploitation by the top who leads the toy into the finding the limits of her personal sexual stamina.
"Hello Fuck Toy, make sure you dress your sluttiest tonight, you are going to be the entertainment at the poker party."
"Yes I love you, but I want you to be a fuck toy for my friends tonight. The guys will be over at 6 P.M."