n. the fundamental drives which govern and affect human behavior. They pertain to the most basic physiological needs of man such as hunger, thirst, sex, and self-preservation. Thus, there is an internal motivation state produced when the person is deprived of the need for food, water, and oxygen or when these supplies are depleted. See drive.

BIOLOGICAL DRIVE: "In order to maintain physiological equilibrium, the biological drive must basically be satisfied."