Source : WordNet®

nonstandard
     adj 1: 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 [ant: {standard}]
     2: varying from or not adhering to a standard; "nonstandard
        windows"; "envelopes of nonstandard sizes"; "nonstandard
        lengths of board" [ant: {standard}]
     3: not standard; not accepted as a model of excellence; "a
        nonstandard text" [ant: {standard}]