Anti-Dumping Duty is an import duty charged in addition to normal Customs Duty and is applied across the whole European Community (EC). It is designed to allow the EC to take action against goods that are sold at less than their normal value - that being defined as the price for ‘like goods’ sold in the exporter’s home market.

https://www.gov.uk/government/publications/anti-dumping-duty-measure-ad2205