youn·gest \-gə̇st\noun (pluralyoungest) Etymology: Middle English yongest, yongeste, alteration (influenced by yong young) of yingest, yingeste, from Old English gyngesta, gyngsta, from gyngst, superl. of geong young : one that is least old; especially: the youngest child or member of a family < you can go back to your law office after our youngest grows up — Evelyn Barkins >