1. Situated nearer the base of a pyramidal organ in relation to a specific reference point; opposite of apical. 2. In dentistry, denoting the floor of a cavity in the grinding surface of a tooth. 3. Denoting a standard or reference state of a function, as a basis for comparison. More specifically, denoting the exact conditions for measurement of basal metabolic rate; basal conditions do not always denote a minimum value, metabolic rate in sleep is usually lower than the basal rate but is inconvenient for standard measurement.