megacycle (meg'-a-cy''-cle). An informal term applied by Mathur (1981b) to strata in the Vindhyan Supergroup of India. Each megacycle "is composed of an orderly and regular superposition of well-defined lithologic units that are of the status of formations and/or members, and the cycle is measured in tens or hundreds of metres." Cf: magnacycle; supercycle (b).