UMBO Meaning of UMBO in English n. (pl. -os or umbones) 1 the boss of a shield, esp. in the centre. 2 Bot. & Zool. a rounded knob or protuberance. umbonal adj. umbonate adj.[ L umbo -onis ] Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012