graf ‧ fi ‧ ti /ɡræˈfiːti, ɡrə-/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Language: Italian ; Origin: graffiare 'to make marks in a surface' ]
rude, humorous, or political writing and pictures on the walls of buildings, trains etc:
The walls are daubed with graffiti.