A type of public marking, either lettering or elaborate wall paintings usually created with spray paint.
Via Art Crimes Website. Graffiti are cross-cultural phenomena common to every literate society. Within the variable contexts of their production, graffiti personalize de-personalized space, construct landscapes of identity, … see full wiki
I love checking out graffiti in cities- no not tagging but, actual pieces. They're art and they often transform a regular old cement building into a piece of art and something of visual interest. I often find myself wondering along walls covered with graffiti and grateful for these outdoor, open, public art galleries. I wish people wouldn't prejudice against these artists and ruin their work by painting over it which often makes it look worse. These artists make the most of what they have in front of them, spray paint and cement and what they do with it is....amazing. So, just because it isn't in acrylic on a canvas, doesn't mean it isn't art!