Natyashastra
कटी मध्यस्य वलनात्च्छिना सम्परिकीर्तिता । पराङ्ग्मुखस्याभिमुखी निवृत्ता स्यान्निवर्तिता ॥ २४७॥
The waist (kaṭi) is termed Chinnā (turned aside) when it is twisted in the middle, and Nivṛttā (turned round) when it turns from being sideways to facing forward.
english translation
kaTI madhyasya valanAtcchinA samparikIrtitA । parAGgmukhasyAbhimukhI nivRttA syAnnivartitA ॥ 247॥
hk transliteration by Sanscript