postmark somethingto place an official mark over the stamp on a letter, etc. that shows when and where it was posted and makes it impossible to use the stamp again邮戳
The card was postmarked Tokyo 9th March.明信片上盖着东京 3 月 9 日的邮戳。
an anonymous letter postmarked in Chicago一封邮戳在芝加哥的匿名信