Definition - What does Sunya mean?
Sunya is a Sanskrit word meaning "zero," "nothing," "empty" or "void." It is derived from the root, svi, meaning "hollow." It is also the root word for sunyata, which means "emptiness" or "nothingness." Sunya is the state of nothingness.
Sunya is related to the ideas of samadhi, amaratva, turya and Brahman.
Yogapedia explains Sunya
The aim of yogic practices is to unite the individual self with Brahman, which is the Absolute Reality. According to Hindu scriptures, Brahman is without attributes; since sunya has zero attributes, Brahman is also referred to as sunya.
According to the "Hatha Yoga Pradipika," oneness of self with the cosmic Self is the state of samadhi, which in itself is the sunya. Practicing yoga and meditation leads the mind to become sunya by releasing the ego, desires and attachments. Understanding sunya leads to such spiritual liberation.
The yogic text, "Shiva Samhita," explains that the yogi who contemplates on sunya is absorbed into space and such contemplation leads to enlightenment.