bhūta-tathatā

(Sanskrit). Term used in Mahāyāna Buddhism to denote the inherent or true nature of phenomena. The term can mean either ‘true suchness’ or ‘the suchness of things’, and is commonly used to contrast the quintessential nature of phenomena with their external appearance. For example, according to the Madhyamaka school, the ‘true suchness’ of objects is emptiness (śūnyatā), whereas they appear to the unenlightened as solid, enduring, and possessed of an individual nature or ‘own being’ (svabhāva). Bhūta-tathatā is thus that which is ultimately real as opposed to the changing forms in which phenomena manifest themselves as they arise and pass away.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)

The bhūtatathatā as understood when the non-individuality or unreality of "things" is perceived.

A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous

Dharma-nature and bhūtatathatā, different terms but of the same meaning.

A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous

The 真如, i. e. bhūtatathatā, is the 體 corpus, or embodiment; the 本覺 is the 相 or form of primal intelligence; the former is the 理 or fundamental truth, the latter is the 智, i. e. the knowledge or wisdom of it; together they form the whole embodiment of the buddha-dharmakāya.

A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous