indecent exposure

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The exposure of one's body, especially the genitals or a woman's breasts, in a public place and in a way considered offensive to established standards of decency.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun law The intentional exposure of the genitals, inner buttocks or female nipples in public (in lands where this is not the cultural norm).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun vulgar and offensive nakedness in a public place