dharma-dhātu (Sanskrit) 1. One of the eighteen dhātus, the objects or contents of the mind.

2. The universal ‘matrix’ which is space-like or empty (śūnya) in nature, from which all phenomena (dharma) arise.

3. The universe itself with all its world-systems and societies of beings.

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