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.Note: The word "defacement" in heraldry and vexillology has none of the bad connotations its other meanings have.