When a female arches her lower back. Usually done in a standing position, bending her knees slightly, sticking her butt out, and forming her lower back into an arch for an erotic pose to get a males attention. (i.e a cat arching its back)
Waitress 1: I just cleaned that window. How did it get so splotched up?
Waitress 2: ...the floss archer over there. He got me in the eye when I refreshed his coffee.