An official certificate, given by the authorities of a port from which a vessel clears, to the master of the ship, showing the state of the port, as respects the public health, at the time of sailing, and exhibited to the authorities of the port which the vessel next makes, in token that she does not bring disease. If the bill alleges that no contagious or infectious disease existed, it is called a “clean” bill ; if it admits that one was suspected or anticipated, or that one actually prevailed, it is called a “touched” or a “foul” bill. 11. In revenue law and procedure, the term is given to various documents filed in or issuing from a custom house, principally of the sorts described below.