1. the basic drive or urge to preserve the species through mating and the activities that precede it or, by extension, simply to express the self and the self’s physiological and psychological needs through sexual activity.

2. in classical psychoanalytic theory, the instinct comprising all the erotic drives and sublimations of such drives. It includes not only genital sex but also anal and oral manifestations and the channeling of erotic energy into artistic, scientific, and other pursuits. In his later formulations, Sigmund Freud saw the sexual instinct as part of a wider life instinct that also included the self-preservative impulses of hunger, thirst, and elimination. Also called sex instinct. See also Eros; libido; self-preservation instinct.