Build your vocabulary with indecent exposure
The car parked next to me opens its door, but no one gets out. Since I'd just as soon not run anyone down as I leave the grocery store, I glance over and see ... some guy staring at me and masturbating in broad daylight. What a world.
I can't imagine it's the reaction the fellow was looking for, but I came home and Googled "exhibitionism". Turns out there's a very specialized vocabulary for describing the act of showing what's normally covered.
Anasyrma refers to lifting the skirt to arouse or shame those watching (but, Wikipedia says, if you're performing anasyrma because you're into it, you're doing it wrong; that's plain old flashing.) Candaulism means exposing someone else for your own sexual arousal, and ought not to be confused with martymachlia, sexual arousal resulting from having others watch a sexual act. (Admittedly, there's little online evidence that anyone actually uses the word "martymachlia" - aside from the single source Wikipedia cites, most of the Google results are just quoting the Wikipedia article.)
Indiana law doesn't divide up indecent exposure the same way. Intriguingly, though, while public nudity without masturbation is usually just a Class C misdemeanor, it ratchets up to Class A if you whip it out on Indiana Department of Natural Resources property. So you're facing six times the jail time and ten times the fines if you try your little open-door act a mile away at Eagle Creek. And I hope your next target has her cell phone handy.