yapokEnglishOxford New American Dictionaryyapok /yəˈpäk, jəˈpɑk / (also yapock) ▸ noun a semiaquatic carnivorous opossum with dark-banded gray fur and webbed hind feet, native to tropical America. Also called water opossum. Chironectes minimus, family Didelphidae. – ORIGIN early 19th century : from Oyapock, the name of a north Brazilian river.