noun (singular graffito /-təʊ/)[treated as singular or plural]
verb[with object] (usually as adjective graffitied)
mid 19th century: from Italian (plural), from graffio 'a scratch'
In Italian the word graffiti is a plural noun and its singular form is graffito. Traditionally, the same distinction has been maintained in English, so that graffiti, being plural, would require a plural verb: the graffiti were all over the wall. By the same token, the singular would require a singular verb: there was a graffito on the wall. Today, these distinctions survive in some specialist fields such as archaeology but sound odd to most native speakers. The most common modern use is to treat graffiti as if it were a mass noun, similar to a word like writing, and not to use graffito at all. In this case, graffiti takes a singular verb, as in the graffiti was all over the wall. Such uses are now widely accepted as standard. A similar process is going on with other words such as agenda, data, and media.