A sadist is a person who is sexually aroused or gains sexual gratification by inflicting pain, cruelty, or humiliation on others. Sadists can also experience the same gratification from watching someone else do these things.
Sadism is believed by some to be a paraphilia or form of sexual disorder in which people gain gratification from objects or situations not normally deemed sexual. Others, however, feel that sadism should not be considered a disorder and can be a safe part of sex play as long as it does not harm or cause distress to either partner.