Definition of YAUPON. : a holly (Ilex vomitoria) of the southeastern United States that has smooth elliptical leaves with emetic and purgative properties.ADVERTISEMENT.Catawba yą́pą, from yą- tree + pą leaf. a holly (Ilex vomitoria) of the southeastern United States that has smooth elliptical leaves with emetic and purgative properties. ADVERTISEMENT. Catawba yą́pą, from yą- tree + pą leaf.