Definitions of pet:

noun: a domesticated animal kept for companionship or amusement
noun: a fit of petulance or sulkiness (especially at what is felt to be a slight)
noun: using a computerized radiographic technique to examine the metabolic activity in various tissues (especially in the brain)
noun: a special loved one
verb: stroke or caress in an erotic manner, as during lovemaking
verb: stroke or caress gently
Example: "Pet the lamb"
adjective: preferred above all others and treated with partiality