संस्‍कृतशब्‍दकोशः

उपनिषद्

पास जाकर नीचे बैठना‚ एकान्त में बैठ कर रहस्य का ज्ञान प्राप्त करना‚ शंकर के अनुसार ब्रह्म ज्ञान के द्वारा अविद्‍या का नाश‚ गुह्य सिद्धान्त‚ रहस्य‚ गुप्त ज्ञान‚ गुप्त ज्ञान की प्राप्ति के लिये उपनिषद् नामक ग्रन्थ

the original meaning of the word seems to be sitting at the feet of the teacher and the secret of life. according to shankaracharya signifies destruction of ignorance by realising the supreme being. though the upanishada generally form part of the brahmanas being continuation of their speculative side, they really represent a new religion, which is in virtual opposition to the ritual and practical side of the veda. their aim is no longer the obtainment of earthly happiness and afterwards bliss in the abode of yama by sacrificing correctly to the gods, but release from mundane existence by the absorption of the individual soul in the world soul through correct knowledge.

Monier–Williams

उपनिषद् — {upa-ni-ṣad} ({upa-ni-√sad}), P. (pf. {-ní-ṣedus}) to sit down near to##to approach, set about AV. xix, 41, 1 ŚBr. Kauś

उपनिषद् — {upa-niṣád} {t} f. (according to some) the sitting down at the feet of another to listen to his words (and hence, secret knowledge given in this manner##but according to native authorities {upaniṣad} means 'setting at rest ignorance by revealing the knowledge of the supreme spirit')##the mystery which underlies or rests underneath the external system of things (cf. IW. p. 35 seqq.)##esoteric doctrine, secret doctrine, mysterious or mystical meaning, words of mystery &c. ŚBr. ChUp. &c##a class of philosophical writings (more than a hundred in number, attached to the Brāhmaṇas {but iiiśopanishad}##their aim is the exposition of the secret meaning of the Veda, and they are regarded as the source of the Vedānta and Sāṃkhya philosophies##for the most important of the Upanishads, IW. p. 37 seq.)