• A restraint placed on an operation to protect the public against a health hazard. A ship may be quarantined so that it cannot leave a protected point. During the quarantine period, the Q flag is hoisted.
  • The period during which a vessel is detained in isolation until free from any contagious disease among the passengers or crew. The word is now applied to the sanitary regulations which are the modern substitute for quarantine. During the quarantine period, the Q flag is hoisted.