Definition of "yellow jack" []

• A yellowish-silver carangid food fish (Caranx bartholomaei) of western Atlantic and Caribbean waters. (noun)
• Nautical A yellow flag hoisted on a ship to request pratique or warn of disease on board. (noun)
• See yellow fever. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Two days later he was carried off to the yellow fever ward, feebly insisting that he must have picked up his yellow jack in Agramonte's dead room or the Las Animas ward."
• "In this way he hoped to prove that yellow jack was spread by mosquitoes, that fomites were harmless, and that the specific agent of the disease was in the blood."
• "The post medical officer was hopelessly incom - petent, and the Commanding Officer refused to believe that he had yellow jack at his camp."