yellow jackEnglishOxford New American Dictionaryyellow jack /ˈyelō jak, ˈjɛloʊ dʒæk/ ▸ noun 1 another term for yellow flag (SENSE 1). 2 archaic term for yellow fever. 3 an edible marine fish with yellowish underparts, found primarily in the Gulf of Mexico and the Caribbean Sea. Caranx bartholomaei, family Carangidae.