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”

Varying from or not adhering to a standard.

“nonstandard windows”

“envelopes of nonstandard sizes”

Not standard; not accepted as a model of excellence.

“a nonstandard text”