What would you call that? Up-ass?
It happened at our nudist resort. We went hiking with a small group around the resort; and at one point there is a steep hill to climb. Being a naughty boy; I ushered my wife forward, ahead of the group, under the guise of helping her keep her balance. Presenting the whole group with an "up-ass" visual. I think she realized what "situation" I was putting her in; but she went right along with it anyway!
The attached pic is obviously not her; but it's a good visual of what the rest of the group was seeing.