Exhibitionism
Exhibitionism is the practice of exposing one's intimate parts – such as the breasts, genitals, or buttocks – in a public or semi-public environment. This can be done live or virtually as with nude selfies using technologies like smartphones to take nude pictures of oneself for show.
Such a display may be innocuous: to friends, acquaintances or strangers for their amusement or sexual satisfaction. It may also be to a bystander to shock them. In the latter case it classically involves men showing themselves to women and goes by legal terms such as indecent exposure or exposing one's person.
Psychologists and psychiatrists are solely concerned with this case and speak of an "exhibitionistic disorder" rather than just "exhibitionism". This is specifically an uncontrollable urge to exhibit one's genitals to an unsuspecting stranger. It is an obsessive-compulsive paraphilic pathology requiring psychiatric treatment.