Yellow Jack Meaning, Definition & Usage

  1. noun caused by a flavivirus transmitted by a mosquito
    black vomit; yellow fever.
  2. noun yellow flag hoist on a ship in quarantine
  3. noun fish of western Atlantic and Gulf of Mexico
    Caranx bartholomaei.

WordNet

Definitions
  1. (Naut.), the yellow fever; also, the quarantine flag. See Yellow flag, under Flag.

Webster 1913