The industry generally refers to such films as adult films, which is part of adult entertainment. Femdom features BDSM scenes in which the dominant partner is female. Lolita pornography features women who are 18 years old or slightly older, who pretend to be underage teen girls. Some may keep their hand stationary while pumping into it with pelvic thrusts in order to simulate the motions of sexual intercourse. Although there may be no connection between coprophilia and sadomasochism , the limited data on the former hentai sex comes from studies of the latter. Female dominance refers to BDSM relationships and BDSM scenes in which the dominant partner is female. Evolutionary psychologists suggest that rounded buttocks may have evolved to be desirable trait because they provide a visual indication of the woman youth and fertility. The term BDSM dates back to 1969; however, the origin of the term BDSM is unclear and is believed to have been formed either from joining the term B&D with S&M , or as a compound initialism from B&D, D&S , and S&M. In some scenes or relationships it may be impossible for consent to be withdrawn in the middle of a scene, or the bottom may have the ability to revoke consent for a relationship as a whole, but not for a particular scene. The term is typically used by the cinematographer within the narrative framework of a pornographic film, and since the 1970s has become a leitmotif of the hardcore genre. The use of the word creampie to describe such scenes originated in U. In the gay pornography gay twink porn industry, which uses amateurs as well as professional actors, the term gay-for-pay refers to actors labeled or believed to be straight but who engage in same-sex sexual activities for money. Lying face down on a comfortable surface such as a mattress or pillow, the penis can be rubbed against it. When used as an alternative to penile-vaginal penetration, the goal may be to preserve virginity or to prevent pregnancy. In Canada, Teletoon offers up its own Teletoon big tit milf at Night programming block.