Definitions of nonstandard:

• adjective:   not standard; not accepted as a model of excellence

  Example: "A nonstandard text"

• adjective:   varying from or not adhering to a standard

  Example: "Nonstandard windows"

• adjective:   not conforming to the language usage of a prestige group within a community

  Example: "A nonstandard dialect is one used by uneducated speakers or socially disfavored groups"