Solecism

[Sarah]

An impropriety or incongruity of language in the
combination of words or parts of a sentence; esp., deviation from the
idiom of a language or from the rules of syntax.

[Mark Zuckerberg]

A nonstandard usage or [grammatical] construction; also, [a minor] [blunder] in speech.

[Dave Paprocki]

A grammatical mistake in speech or writing.

[Couch Potatoe]

behaviour that is a social mistake or is not polite: