Toy in graffiti is a term commonly used for a unskilled writer. Usually an experienced artist will tag the work with toy. Often artists will begin as toys but some are too old to remember what it was like. Over time you develop your style and maybe lose your toy status.
Lush in Fitzroy
Showing strong disrespect to artist by writing on the piece.
Turf war with toys
One artist has called a piece a toy and then another artist has said "NO WAY".