A disorder in which fantasies about or the act of exposing the genitals to an unsuspecting stranger produces sexual excitement with no attempt at further sexual activity with the stranger.
Paraphilias
Disorders that include recurrent, intense sexually arousing fantasies, sexual urges, or behaviors generally involving nonhuman objects, suffering of oneself or partners, or children or other nonconsenting partners. (from DSM-IV, 1994)