Clothed male, naked female is one-sided female nudity in which one or more females are nude while one or more men are clothed. 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 invited to induce orgasm. Female ejaculation is the expulsion of fluid by the paraurethral ducts through and around the human female urethra during or before an orgasm. Female dominance refers to BDSM relationships and BDSM scenes in which the dominant partner is female. Preggo pornography features pregnant performers and may include erotic lactation as a fetish. The definition clash also appears with the English definition of yuri as any lesbian relationship, as opposed to its sexually explicit definition in Japan. A homosexual threesome would involve either three gay boy porn men or three women. Macrophilia is a fascination with or a sexual fantasy involving giants, more commonly expressed as giantesses . Many cultures describe pain as an aphrodisiac. Mammary intercourse is known as titty-fucking, titfuck, or a titjob in the United States, as well as tit wank or French fuck in the United Kingdom - the latter term dating back to the 1930s; while a more jocular equivalent is a trip down mammary lane. Typically featured are hitting, choking, name-calling and hair-pulling. Bestiality is illegal in many countries. 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. Double Stuffed , Double Vaginal , or Double Anal pornography involves the penetration of one orifice by two penises or other objects. When the interest in a particular subject is obsessive, the behavior may be described as stalking. Rainbow party A rainbow party is an urban legend spread from horny milfs the early 2000s. Normal quantities of ejaculate range from 1.5 to 5.0 milliliters . Interactive pornography, available in CD-ROM and DVD format, allows the viewer to select the particular acts performed at any one time, hentai porn sometimes with the camera providing a first person view.