noun a cleaving, splitting, or breaking up into parts.
2. fission ·noun a process by which certain coral polyps, echinoderms, annelids, ·etc., spontaneously subdivide, each individual thus forming two or more new ones. ·see strobilation.
3. fission ·noun a method of asexual reproduction among the lowest (unicellular) organisms by means of a process of self-division, consisting of gradual division or cleavage of the into two parts, each of which then becomes a separate and independent organisms; as when a cell in an animal or plant, or its germ, undergoes a spontaneous division, and the parts again subdivide. ·see segmentation, and cell division, under division.