++ [ originally posted by Don Bes ] ++
the Encarta Dictionary defines stud as
equestrian breeding stallion: a male animal, especially a stallion, used for breeding
sexually active man: a man considered to be sexually active or good at sex (informal)
equestrian establishment with stallions: a stable or farm where male animals, especially stallions, are kept for breeding
equestrian group of stallions: a group of male animals, especially stallions, used for breeding