If you twist your body into a contortion, you might put one leg behind your ear, and clasp your arms behind your back. A contortion is a twisted position.
Yoga can feel like a series of contortions to beginners. People who twist their bodies into contortions professionally are called contortionists. In order to become a contortionist, you need to start with a lot of flexibility and a willingness to contort your body into uncomfortable positions. You then need a lot of practice. It is not easy to achieve a perfectly freakish contortion.