a yellow flag, designating the letter Q in the International Code of Signals: flown by itself to signify that a ship has no disease on board and requests a pratique, or flown with another flag to signify that there is disease on board ship.
Main Entry: quarantine flag Function: noun : a yellow flag hoisted by all ships to request pratique on entering a harbor, by a ship to show that it has contagious orinfectious disease aboard, or by a ship that has been quarantined called also yellow flag,yellow jack
