Deface

verb

1. To damage or vandalize something, especially a surface, in a visible or conspicuous manner.

   "After the painting was defaced a decade ago, it went viral and has been a tourist attraction ever since."

2. To void or devalue; to nullify or degrade the face value of.

   "He defaced the I.O.U. notes by scrawling "void" over them."

3. (flags) To alter a coat of arms or a flag by adding an element to it.

   "You get the Finnish state flag by defacing the national flag with the state coat of arms placed in the middle of the cross."