a woman who subjects her masochistic sexual partner to bondage, the infliction of ritualistic punishments, etc.; specif., a prostitute who performs such acts for her customers
See dominatrix in American Heritage Dictionary 4
(dŏmˌə-nāˈtrĭks)
nounpl.dom·i·na·trix·es or dom·i·na·tri·ces(-nāˈtrĭ-sēzˌ, -nə-trīˈsēz)
A woman who acts out the role of the dominating partner in a sadomasochistic relationship.