When a hand gun is held over the head, with the hand oriented palm down, so that the gun is on its side.
This is called the flounder grip, as the sites will eventually migrate to the side of the slide, and once again be on the top, much like a flounder's eyes migrate to the side of the flounder's head so that the eyes are both on top.
See any armed robbery movie footage, or flounder photos from nature documentaries.

"The bank robber was holding the gun in a flounder grip, surely to stike fear in his victims with his certainty of aim."
by William Maderas May 8, 2008
Get the flounder grip mug.