see PlainEnglish

I cringe whenever I hear it. Typically arises in contexts of stereotyping and pseudo-intellectual/pseudo-moral judgment. A concept best translated as Good Breeding, with all that implies.

It's used mainly to characterize English that is inoffensive, as distinct from swearing, slang, nonsensical English, etc., that is offensive to many people, or at least indicative that the speaker poor communication skills.