Rarely used N length chain of words.
I.e. a high frequency 3-gram is "by the way".
A low frequency 3-gram is "elephants speak french".
But if you go too far the other direction, too many common n-grams, then it becomes platitude-speak, and nobody wants to read that either.
But if you go too far the other direction, too many common n-grams, then it becomes platitude-speak, and nobody wants to read that either.