mangosteen Syllabification: (man·go·steen)Pronunciation: /ˈmaNGgəˌstēn/Definition of mangosteen noun 1a tropical fruit with sweet juicy white segments of flesh inside a thick reddish-brown rind. 2the slow-growing Malaysian tree that bears the mangosteen fruit. Garcinia mangostana, family Guttiferae Origin: late 16th century: from Malay manggustan, dialect variant of manggismangosteen in other Oxford dictionaries Definition of mangosteen in the British & World English dictionary