yellow jack

noun

, plural (especially collectively) yel·low jack, (especially referring to two or more kinds or species) yel·low jacks

1. Informal. quarantine flag.
2. Pathology. yellow fever.
3. any carangoid fish, especially a Caribbean food fish, Caranx bartholomaei.

yellow jack

noun

1. pathol another name for yellow fever
2. another name for quarantine flag
3. any of certain large yellowish carangid food fishes, esp Caranx bartholomaei, of warm and tropical Atlantic waters

Word History and Origins

Origin of yellow jack¹

An Americanism dating back to 1830–40