A pose where you place your chest on the ground, and curve your back upwards and over until both of your legs are in front of your head.
In Japanese, this is known as the "King Aladdin Impression" (キングアラジンの真似, King Aladdin no Mane), after King Aladdin, the villain in the first episode of the horror TV drama, Operation: Mystery! (怪奇大作戦, Kaiki Daisakusen). In the drama, he rolls away in the chest stand position, and laughing, disappears into the wall as though being plastered into it.
More recently, this pose has also been called the Gundam Epyon Mobile Armour Mode. The Gundam Epyon in the Gundam Wing is able to transform into what looks like a two-headed dragon. This design is meant to be breathtaking when seen from above but from below, you can really understand how it just looks as though it's doing a simple chest stand.
