(or 優波尼沙陀)Upaniṣad, also (優婆尼沙曇; certain philosophical or mystical writings by various authors at various periods 'attached to the Brāhmaṇas, the aim of which is the ascertainment of the secret of theVeda(they are more than a hundred in number, and are said to have been the source of the sixdarśanas, or systems of philosophy)'. M.W. The best known is theBṛhad-āraṇyaka.