WordNet sense 1 ((genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants)):

meiosis, reduction division

WordNet sense 2 (reflex contraction of the sphincter muscle of the iris in response to a bright light (or certain drugs) causing the pupil to become smaller):

myosis, light reflex, pupillary reflex