Privacy means to be secluded from the sight, presence or intrusion of others. The adjective private is an opposite to public.
Privacy for sexual activities
One, two or more people may engage in a variety of acts in private, which means others are not watching. A husband and wife often have sexual intercourse in private. Thus, their sex lives take place behind the closed door of a bedroom. Masturbation is usually done in privacy, too. Even a sexual orgy is private because all present are participating with one another.
To ensure privacy, doors can be locked and windows can be closed.
Privacy in spanking and BDSM
In consensual spanking, private or public spankings may be given. The spankee may feel humiliation in private, but such feelings are heightened in public. In such an act, watchers observe as the buttocks are bared, displayed and spanked. Such a scene may be sexaully arousing to some, including the spankee.
"Reserved for one's exclusive use" is another meaning of private, e.g. a private home. In the BDSM context, a slave may be reserved for its Master's exclusive use. Thus, the slave is no longer available to a 3rd party. Essentially, a submissive agrees to be taken by a Master as private property. A Master may own other slaves, but a slave is bound in servitude.
- More information on this topic is available at [ Wikipedia:Privacy ]