miosis

Noun

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

• (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)

Related words

• Synonyms: 
  light reflex , pupillary reflex , myosis , meiosis , reduction division