Sorry, I did overlook that post.
f16man is correct. A lomcevak (sometimes spelled lomcovak) is an aerobatic maneuver where the plane tumbles end over end. A "lomcevak duck" is what people on the ground do when a pilot attempts a new maneuver for the first time and people in the pits "duck" or run to get out of the way.
Usage: "Pete tried a new 3D maneuver, but ended up losing the plane in the pits. We all did the lomcevak duck and scattered before his plane hit my truck."
My avatar is a duck tumbling end-over-end that I drew while pretending to pay attention in a music appreciation class a little more than a decade ago.
http://en.wikipedia.org/wiki/Lomcovak