Brahman, in Hinduism, means the Supreme Realty conceived of one and undifferentiated, static and dynamic, yet above all definitions; the ultimate principle which underlies the world, the ultimate realty. The concept of Brahman almost defies definition, and continually changes throughout the eons. Brahman is now more philosophical, reverting from an active principle as it was in past ages to a passive one, to be meditated upon but not adored and worshiped.
The philological aspects of Brahman are important. The root of the word is brh (to make, to form, to grow). The term brahman meant at first prayer, hymn, magical formula, sacred knowledge (and still means sacred word in some contexts), then the power in them, and finally the Supreme Power. The pronunciation of brahman changes its meaning from sacred utterance to one imbued with the power of sacred speech, or of the sacred word. Brahman came to denote both the creator, or Absolute, divine substance and a man, the latter being a brahman (commonly spelled brahmin in English to lessen confusion), who is of the priestly caste, which is the first social order, or varna, in Hindu society. The term creates confusion if the stress and shifts in pronunciation are not noticed and observed; however the meanings meld into each other, for each is intimately part of the other, and yet separate.
The central, or full, concept of Brahman is indescribable; all words used in connection with Brahman are neuter, which means Brahman is pure concept. IT, not He, is neither a god, nor pure spirit, nor a thing or object. Brahman is an inexhaustible plentitude, a measureless reservoir, both fullness and emptiness. Although Brahman can be inadequately described as primeval Matter and Spirit alike, both external principles, there is no absolute separation. To designate Brahman as “the Ground of All Being,” as Western vedantists do, is to belittle the immensity of Brahman. The term Nirguna Brahman is sometimes used. In summary, Western terms used to describe Brahman fail because there is no tangible description or definition. Brahman is silence, according to Samkara (c. 788-820 AD), Nada Brahman. “‘Sir,’ said a student to his master, ‘teach me the nature of Brahman.’ The master did not reply. When he was asked a second and a third time, he replied: “I teach you, but you do not listen. His name is silence.'”
The mythical image of Brahman, in the Vedas, as sound or word is the skambha, the cosmic pillar that supports the world; skambha is also the cosmic axis and ontological foundation. Also, Brahman is expressed by the monosyllable OM, pregnant with the meaning of eternal words, within which all other sounds are contained. Visually Brahman is signified by yantra, the graphic equivalent of the symbols of creation. In the overlapping triangles that form the center of a yantra, symbolizing the union of male and female, the central point (or bindu) signifies the undifferentiated Brahman. In certain aspects of Tantra, the coupling (or samhita) of man and woman expresses the union with the gods and with Brahman. A.G.H.
Source: 83, 71-73.