bhavāṅga, life continuum. The consciousness one experiences in a dreamless state is known as bhavāṅga. This type of consciousness is akin to that which one experiences at the moments of conception and death. Bhavāṅga is the essential condition for a continued existence. It refers to the vital continuum in the absence of any process of mind or attention. Bhavāṅga is the current that forms the condition of being or existence, the indispensable condition of life; the function of being, or the functional state of subconsciousness. Bhavāṅga is the foundation of existence that is in the form of continuity -- a process or a flux. It arises and perishes every moment, flowing like a stream which is not the same for two consecutive moments.

     Bhavāṅga thought -- moments occur more frequently than any other type of consciousness. The bhavāṅga consciousness vibrates for a thought-moment and it passes away when a physical or mental object occurs to the mind. The current that is the essential condition of being or existence is known as bhavāṅga sota whereas the subconscious life is known as bhavāṅga citta.

Buddhānusmṛti - A Glossary of Buddhist Terms

Aṭṭhasālinī. I. 378, 380-381, 383, 385, 405. A Comprehensive Manual of Abhidhamma. III. 122-123; IV. 174. Majjhima Nikāya. Mahāhatthipadopama, Mahātaṇhāsaṅkhaya.

bhavāṅga

(Pāli). Concept evolved primarily in Pāli Abhidharma commentarial literature in order to explain the continuity of consciousness and personal identity in the absence of a permanent self (the latter being denied by the anātman doctrine). The bhavaṇga is the individual's ‘life continuum’ which flows on like a stream (sota) from one existence to the next. Sometimes known as the bhavaṇga-citta, or ‘consciousness continuum’, it is the foundation of all experience, both conscious and unconscious. It retains the traces of all impression and sensations, and makes it possible to have recollections of these in the form of memories. At the beginning and end of each individual existence it is known as ‘rebirth-linking consciousness’ (paṭisandhi) and ‘death consciousness’ (cuti-citta) respectively. The concept of the bhavaṇga paved the way for later idealist trends and the evolution of the notion of the ālaya-vijñāna or ‘storehouse consciousness’.

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