Wariza (割座), also known as "w-sitting" or "reverse tailor style sitting" in English, is a sitting posture whereby the butt is on the floor and the legs are bent backwards on each side of the body. It is the traditional informal sitting style for Japanese women. If the legs are folded out to only one side, then it is called yokozuwari.
All examples here.

See also

• sitting
• seiza
• yokozuwari