eu-gen-ics (yōō-jěn’ĭks) noun. the study of or belief in the possibility of improving the qualities of the human species or a human population, especially by discouraging reproduction by persons having genetic defects or presumed to have inheritable undesirable traits (negative eugenics) or encouraging reproduction by persons presumed to have inheritable desirable traits (positive eugenics). Origin: 1883, from Greek "well-born."