Graffiti is artistic vandalism. It is a form of creative expression characterized by the act of defacing public or private property. the term refers to images or artistic lettering scratched, scrawled, painted, or marked on property generally not owned by the graffitist. Graffiti is an issue surrounded by a great deal of controversy regarding its validity and legality; many consider graffiti to be a progressive and meaningful art-form while others regard it as unwanted, unsightly damage to personal property.
Look at that gorgeous mural, the artist must be incredibly talented. He turned that boring brick wall into an artistic masterpiece.
Graffiti isn't art, it's vandalism. That boring brick wall was not his to paint.