Noun
a rude decoration inscribed on rocks or walls
Source: WordNetIn the late 1980s the upside down Martini glass that was the tag for punk band Missing Foundation was the most ubiquitous graffito in lower Manhattan, and was copied by hard core punk fans throughout the US and West Germany. Source: Internet
A popular graffito of the 1970s was the legend "Dick Nixon Before He Dicks You", reflecting the hostility of the youth culture to that US president. Source: Internet