Tribaism or tribbing is a form of mutual masturbation, sometimes called frottage, in which a woman rubs her vulva against her partner's body for sexual stimulation. The term is most often used in the context of lesbian sex, but is not exclusive to lesbians. Tribadism sometimes involves female-to-female genital contact, but more often refers to a female rubbing her vulva against her partner's thigh, arm or stomach. Tribadism can also refer to a masturbation technique in which a woman rubs her vulva against an inanimate object such as a bolster in an effort to achieve orgasm.