Nirvana, in Hinduism, is the Union with the Supreme Brahman (God) through moksa, the release from the cycle of birth and death as well as pain, sorrow, and suffering within the human condition of life. Nirvana is the immediate experience of ego-less with the blissful Brahman.
The Bhagavad-Gita has one of the clearest expositions of nirvana, calling it Brahma-nirvana, that is, union with Brahman, or extinction (of the ego) in Him. The obtaining of the Gita’s is by the practice of yoga (joy, peace, vision all turning inward), through which one can “come to Brahman and know nirvana.”
Rice, Edward, Eastern Definitions: A Short Encyclopedia of Religions of the Orient, Garden City, New York, Doubleday, 1978, p. 277