Emptiness is a Buddhist term that is translated into English as emptiness, openness, thusness, etc. Śūnyatā refers to the absence of inherent existence in all phenomena, and it is complementary to the Buddhist concepts of no-self and Dependent origination.
In Tai Chi, the state of emptiness is an essential step, in the process of mastering Tui Shou and the highest level (松空 Song Kong - Empty "Song") of the 6 Levels of Song.
Theravada Buddhists generally take the view espoused in the Pali canon, that emptiness is merely the not-self nature of the five aggregates as well as a mode of perception which is "empty of the presuppositions we usually add to experience to make sense of it" - especially that of unchanging selfhood. Therefore, Theravadan teachers like Thanissaro Bhikku hold that emptiness is not so much a metaphysical view, as it is a strategic mode of acting and of seeing the world which leads to liberation:
The idea of emptiness as lack of inherent existence has very little to do with what the Buddha himself said about emptiness. His teachings on emptiness — as reported in the earliest Buddhist texts, the Pali Canon — deal directly with actions and their results, with issues of pleasure and pain. To understand and experience emptiness in line with these teachings requires not philosophical sophistication, but a personal integrity willing to admit the actual motivations behind your actions and the actual benefits and harm they cause.
Emptiness as an approach to meditation is seen as a state in which one is "empty of disturbance." This form of meditation is one in which the meditator becomes concentrated and focuses on the absence or presence of disturbances in their mind, if they find a disturbance they notice it and allow it drop away, this leads to deeper states of calmness.
Emptiness is also seen as a way to look at sense experience that does not identity with the "I-making" and "my-making" process of the mind. As a form of meditation, this is developed by perceiving the six sense spheres and their objects as empty of any self, this leads to a formless jhana of nothingness and a state of equanimity.
See also: Middle Way
A nihilistic interpretation of the concept of voidness (or of mind-only) is not, by any means, a merely hypothetical possibility; it consistently was adopted by Buddhism's opponents, wherever the religion spread, nor have Buddhists themselves been immune to it...
But this is not a correct understanding:
[V]oidness does not mean nothingness, but rather that all things lack intrinsic reality, intrinsic objectivity, intrinsic identity or intrinsic referentiality. Lacking such static essence or substance does not make them not exist —- it makes them thoroughly relative.
Conversely, emptiness as described by Nāgārjuna has been interpreted, notably by Murti in his influential 1955 work, as a Buddhist absolute. This is now regarded as incorrect by many modern scholars and not grounded on textual evidence. The consensus is that Nāgārjuna defended the classical Buddhist emphasis on phenomena. For him, emptiness is explicitly used as a Middle Way between eternalism and nihilism, and that is where its soteriological Power lies. It does not specifically refer to an ultimate, universal, or absolute nature of reality. Holding up emptiness as an absolute or ultimate truth without reference to that which is empty is the last thing either The Buddha or Nāgārjuna would advocate.
Nāgārjuna criticized those who conceptualized emptiness:: The Victorious Ones have announced that emptiness is the relinquishing of all views. Those who are possessed of the view of emptiness are said to be incorrigible.
TaiChi Metaphysics Buddhism