An individual adopting a position in which its weight is supported by its rump and forefeet. A sitting elephant may often raise its trunk over its head allowing it to flop back on its head in a kind of Head-Toss. It may repeat these actions several times.  

References:  Poole & Granli 2011 (Full reference list)

This behavior occurs in the following context(s): Lone & Object Play, Social Play