Definition of nonstandard

• not conforming to the language usage of a prestige group within a community; "a nonstandard dialect is one used by uneducated speakers or socially disfavored groups"; "the common core of nonstandard words and phrases in folk speech"- A.R.Dunlap
• varying from or not adhering to a standard; "nonstandard windows"; "envelopes of nonstandard sizes"; "nonstandard lengths of board"
• not standard; not accepted as a model of excellence; "a nonstandard text"