Blithering is almost never used on its own. You will hear it in front of idiot: a blithering idiot — someone who has done something thoroughly stupid. For most speakers it is no longer really about talking; it is just a strong, slightly old-fashioned, mostly British intensifier. It is informal and rude if you aim it at a real person. Older speakers and comedy still use it; many younger people barely say it. It does not belong in careful school writing. You might also see blithering as a verb form, “talking on with little sense,” but the insult is the use students actually meet.

愚蠢透頂的（幾乎只出現在 blithering idiot；不要譯成「喋喋不休」）