meiosis
n. a special type of division of the cell nucleus that occurs during the formation of the sex cells (ova and spermatozoa). During meiosis, a parental cell in the gonad produces four daughter cells that are all haploid; that is, they possess only one of each chromosome, instead of the normal diploid complement of homologous pairs of chromosomes. During the process of fertilization, the ova and spermatozoa undergo fusion, which restores the double set of chromosomes within the nucleus of the zygote thus formed. Compare mitosis.