‖n. [ NL., fr. Gr. ka`ryon a nut, kernel + kinei^n to move. ] 1. (Biol.) The indirect division of cells in which, prior to division of the cell protoplasm, complicated changes take place in the nucleus, attended with movement of the nuclear fibrils; -- opposed to karyostenosis. The nucleus becomes enlarged and convoluted, and finally the threads are separated into two groups which ultimately become disconnected and constitute the daughter nuclei. Called also mitosis. See Cell development, under Cell. [ 1913 Webster ]

2. The changes that occur in the nucleus of a cell, especially movements of the chromosomes, in the process of cell division. [ PJC ]