Definition of Miosis

Noun: miosis (mioses) mI'ow-sis

(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
Reflex contraction of the sphincter muscle of the iris in response to a bright light (or certain drugs) causing the pupil to become smaller
- light reflex, pupillary reflex, myosis