Horse feathers is a slang term that means nonsense or something that is not worth believing. There are several synonyms that can be used instead of horse feathers, depending on the context of the situation. Some of the most common synonyms for horse feathers include baloney, hogwash, rubbish, bunk, claptrap, twaddle, and poppycock. These words can be used interchangeably to describe something that is unbelievable or nonsensical. Other synonyms for horse feathers include malarkey, fluff, drivel, and tripe. Regardless of which synonym is used, the meaning is clear: the topic being discussed is not worth taking seriously.