Definition

A graffiti artist's signature or personal logo, usually executed quickly with spray paint to mark territory or build recognition. Tags are the fundamental unit of street art culture, ranging from simple stylized names to complex artistic statements. Think of them as permanent autographs on the urban landscape.

Example Usage

That tagger's signature is all over the subway line—must have hit twenty cars last night.

Source: Urban Dictionary (https://www.urbandictionary.com/define.php?term=tag&defid=13378)