Engineering: Ground, in audio terminology, usually refers to the metal chassis of the equipment. In the electrical sense, ground is the reference point from which most voltage measurements are made. When a technician measures the amount of voltage applied to a tube, for example, he attaches one wire from his voltmeter to the appropriate tube pin and the other to the chassis, or ground. [Fantel, Hans; The True Sound of Music - A Practical Guide to Sound Equipment for the Home; 1973, E. P. Dutton & Company, Inc., New York]
Spiritual: Close or clear connection to earth. Balance. Stability. Take on earth or terrestrial polarity.
See Also
Cosmic microwave background
Depolarize
grounding
Universal Ground State
Voiding