Blithering idiocy, a term used to describe foolish or nonsensical behaviour, has several synonyms that can be used interchangeably. Some of these synonyms include absurdity, foolishness, nonsense, idiocy, irrationality, and stupidity. While each of these words conveys a similar meaning to blithering idiocy, they can be used in different contexts to emphasize different aspects of foolish behaviour. For instance, absurdity might be used to convey how ludicrous or illogical something is, while idiocy might be used to emphasize the lack of intelligence. In any case, these synonyms provide a range of options for expressing your frustration at someone's foolish behaviour.