Any professional misconduct.
Source: U.S. Courts
A carrier giving a customer illegal preference to attract cargo. This can take the form of a money refund (rebate); using lower figures than actual for the assessment of freight charges (undercubing); misdeclaration of the commodity shipped to allow the assessment of a lower tariff rate; waiving published tariff charges for demurrage, CFS handling or equalization; providing specialized equipment to a shipper to the detriment of other shippers, etc.
Source: U.S. Maritime Administration.