Individuals are also sometimes abbreviated when referred to in writing, so a dominant person may be referred to as a Dom for a man, and a Domme for a woman. Dwarfs or midget pornography features performers who are dwarfs/midgets. In general, hentai movies BDSM play is usually structured such that it is possible for the consenting partner to withdraw his or her consent during a scene; for example, by using a safeword that was agreed on in advance. As of 2013, little analysis of this big tit milf paraphilia has been reported in medical literature. For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. There has been an increase in discussion and portrayal of masturbation in art, popular music, television, films, and literature. Transsexual porn star Wendy Williams has stated that transsexual Porn is classified as Straight Specialty. Pornography is often distinguished from erotica, which consists of the portrayal of sexuality with high-art aspirations, focusing also on feelings and emotions, while pornography involves the depiction of acts in a sensational manner, with the entire focus on the physical act, so as to arouse quick intense reactions. The wife who enjoys cuckolding her husband is frequently called a hotwife, or a cuckoldress if the man is more submissive. A female dominant in a master/slave relationship is often termed a Mistress, not to be confused with the colloquial usage of mistress as a kept sexual partner without a similarly formalized power relationship. This stop and go build-up, known as edging, can achieve even stronger orgasms. It is mutual consent that makes a clear legal and ethical distinction between BDSM and such crimes as sexual assault or domestic violence. Jerk off instruction features a performer encouraging or instructing the viewer to masturbate, often culminating in a countdown at the end of which the viewer is gay twinks invited to induce orgasm.