"Horse feather" is an obscure term that means nonsense or something of little importance. Some synonyms for this term include balderdash, bunkum, drivel, gibberish, hogwash, malarkey, and poppycock. These words are often used to describe speech or writing that lacks substance or relevance. Other similar phrases that can be used interchangeably with horse feather include "rubbish," "tommyrot," and "flapdoodle." These words and phrases are often used to dismiss an argument or statement that is not valid or relevant. Whatever phrase you use, it's clear that the idea being presented is not worth considering seriously.