letter of marque
noun
(一般作letters of marque)
1- historical a licence to fit out an armed vessel and use it in the capture of enemy merchant shipping and to commit acts which would otherwise have constituted piracy〈史〉船只武装特许证（战时特许船只装备并使用武器以便俘获敌方商船的许可证, 凭此证还可采取在无证情况下被视为海盗行为的其他行动）。
1.1
- a ship carrying such a licence特许证船只。
词源
late Middle English: Law French marque, from Old French marque 'right of reprisal'.