(It. quaranto, forty), is a trial which ships must undergo when suspected of pestilential infection. It may be ordered by her Majesty, with advice of the Privy Council, at such times and under such regulations as she judges proper. Ships ordered on quarantine must repair to the place appointed, and continue there during the time prescribed; and they must carry a yellow flag at the main, and have no intercourse with the shore except necessary provisions, which are conveyed with every possible precaution. When the time is expired, and the goods have been opened and exposed to the air as directed, if there be no appearance of infection, they are admitted to port. This check to infection was first used by the Venetians. (See Plague; also M'Culloch's Comm. Dictionary.)