Bondage/BDSM Bondage pornography features performers tied up or constrained in various ways. If this is gay sex video done using penises and/or strap-on dildos, this is sometimes called the sandwich or BigMac. Snowballing or snowdropping is the human sexual practice in which one person takes someone else semen into his or her mouth and then passes it to the mouth of the other, usually through kissing. 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. It is geared towards heterosexual men, who most typically define a threesome as such. In S/M, the Sadist is usually the Top and the Masochist the Bottom, but these roles are frequently more complicated or jumbled . It contains graphic sexual activity and visible penetration. Men may also rub or massage the glans, the rim of the glans, and the frenular delta. Since mammary intercourse is a non-penetrative sex act, the risk of passing a sexually transmitted infection that requires direct contact between the mucous membranes and pre-ejaculate or semen is greatly reduced. There are number of types of sex parties: Swinger party/gathering A swinger party or partner-swapping party is a gathering at which individuals or couples in a committed relationship can engage in sexual activities with others as a recreational or social activity. BDSM communities generally welcome anyone with a non-normative streak who identifies with the community; this may include cross-dressers, extreme body mod enthusiasts, animal players, latex or rubber aficionados, horny milfs and hentai sex others. Pornography may fall into more than one genre. The existence of such content in commercially available pornography is widely considered an urban legend. The term pearl necklace is used by some because the drops of semen deposited by the man resemble a necklace of translucent white pearls. Commercialized pornography accounts for a nearly US0 billion worldwide industry for the production of various media and associated products and services.