Green’s Dictionary of Slang

(US black/teen) to destroy another graffiti artist’s work by drawing over it; thus toy someone out; as n., one who is inferior in the hierarchy of graffiti artists.

1982		C. Castleman Getting Up: Subway Graffiti In N.Y. 76: The word toy is used by writers to refer to anything insignificant […] especially, toys is used to describe inferior or inexperienced writers.
2001		N. Macdonald Graffiti Subculture xii: Toy: A young, inexperienced or artistically incompetent writer.
2003		J. Lethem Fortress of Solitude 362: FMD and DMD members, the gangs who’d toyed our own feeble tags out of existence. [Ibid.] 444: I was a toy I know — you was right to go over my tags.
2004		Observer Cash 3 Oct. 10: All that was needed to spark a beef was ‘toy’ sprayed by a rival over an artist’s ‘tag’ [...] ‘Toy’ meant: ‘I don’t like your shit,’ says Stash.