A marching step of 15 inches (38 centimeters) at quick time and 18 inches (46 centimeters) at double time.
sem·i·tone (sěm'ē-tōn', sěm'ī-) n.
Music An interval equal to a half tone in the standard diatonic scale. Also called half step, halftone. sem'i·to'nal adj., sem'i·to'nal·ly adv.