Verb

1. To damage something in a visible or conspicuous manner.
   • 1869: George Eliot, The Legend of Jubal

     That wondrous frame where melody began / Lay as a tomb defaced that no eye cared to scan.

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

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

   • 1776: Adam Smith, The Wealth of Nations

     One-and-twenty worn and defaced shillings, however, were considered as equivalent to a guinea, which perhaps, indeed, was worn and defaced too, but seldom so much so.

Synonyms

• (damage in a conspicuous way): disfigure, mar, obliterate, scar, vandalize
• (degrade the face value): cancel, devalue, nullify, void