Definify.com

Webster 1913 Edition

Noun.

The act of defacing, or the condition of being defaced; injury to the surface or exterior; obliteration.

That which mars or disfigures.

Bacon.

defacement ‎(plural defacements)

An act of defacing; an instance of visibly marring or disfiguring something.
Some consider the defacement of the Sphinx to be the most egregious crime of Napolean's campaigns.
An act of voiding or devaluing; nullification of the face value.
The soldiers found a variety of creative uses for their payment scrip after its defacement to scrap paper; some used it as toilet paper.
(heraldry, vexillology) A symbol added to a flag or coat of arms to change it or make it different from another.

Defacement generally has negative valence (that is, it is a bad thing), except in heraldry, where it is a neutral term.

marring, disfiguring

voiding, nullification

added symbol