be not the word for it
Of a word or phrase, to not fully or adequately describe something. Angry? Angry isn't the word for it—I'm blinded with rage! Bad isn't the word for what they've done. It's despicable.
not be the ˈword for it
used to say that a word or an expression does not describe something fully or strongly enough: Unkind isn’t the word for it! I’ve never seen anyone treat an animal so cruelly!