Basal Metabolism Definition

The minimum quantity of energy used or required to sustain life in an organism at rest: it is measured, in people, by the rate (basal metabolic rate) at which heat is given off by a conscious, resting person in a warm place 12 to 18 hours after eating, and is expressed in large calories per hour per square meter of skin surface.
Webster's New World
The minimum amount of energy required to maintain vital functions in an organism at complete rest, measured by the basal metabolic rate in a fasting individual who is awake and resting in a comfortably warm environment.
American Heritage Medicine