One who gets pleasure (often sexual) from the suffering of others. It is a common myth that sadists like masochists, however the true sadist can get no pleasure from the pain he causes the masochist because the masochist is enjoying it.
*Masochist sees a sadist (identified by the whip and handcuffs in his back pocket) and sees an opportunity for a beautiful relationship*
Masochist: HURT ME!!!