Meaning

noun (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 anim

noun understatement for rhetorical effect (especially when expressing an affirmative by negating its contrary)

originFrom Ancient Greek μείωσις (meíōsis, “a lessening”), from μειόω (meióō, “I lessen”), from μείων (meíōn, “less”). The biological sense was coined by British biologists John Bretland Farmer and John Edmund Sharrock Moore in 1905 as maiosis in a paper in the Quarterly Journal of Microscopic Science, with the spelling corrected on etymological grounds later that year. Doublet of miosis.

Etymology from Wiktionary, CC BY-SA 3.0