Nirvikalpa is a Sanskrit adjective with the general sense of "not admitting an alternative", formed by applying the contra-existential prepositional prefix निः ("away, without, not") to the term विकल्प ("alternative, variant thought or conception")
In Buddhist philosophy, the technical term nirvikalpa-jñāna is translated by Edward Conze as "undifferentiated cognition". Conze notes that only the actual experience of nirvikalpa-jñāna can prove the reports given of it in scriptures. He describes the term as used in Buddhist context as follows:
The "undiscriminate cognition" knows first the unreality of all objects, then realizes that without them also the knowledge itself falls to the ground, and finally directly intuits the supreme reality. Great efforts are made to maintain the paradoxical nature of this gnosis. Though without concepts, judgements and discrimination, it is nevertheless not just mere thoughtlessness. It is neither a cognition nor a non-cognition; its basis is neither thought nor non-thought.... There is here no duality of subject and object. The cognition is not different from that which is cognized, but completely identical with it.
A different sense in Buddhist usage occurs in the Sanskrit expression nirvikalpayati (Pali: nibbikappa) that means "makes free from uncertainty (or false discrimination) = distinguishes, considers carefully
highest samadhi, the one called "neither cognition nor non-cognition.