/ˈkʌstəmz siːl/ – Phrase
Definition: con dấu hải quan
A more throughout explanation: a thin piece of paper, metal, plastic, or other material that covers the opening of a box of goods and which must be broken in order to open the box. This is attached to the box to show that the contents have passed through customs and can be brought into a country.
Example: He is accused of illegally breaking a customs seal.