"Brass neck" is an idiom that describes an individual who is excessively bold or shamelessly rude. Synonyms for this phrase include "nerve," "gall," "audacity," and "impudence." Other options include "cheek," "chutzpah," "temerity," and "effrontery." These words are often used interchangeably and convey a similar idea - someone who is willing to act in a way that is offensive or disrespectful without any sense of guilt or shame. Recognizing these synonyms can enhance one's vocabulary and provide alternatives for expressing emotions of frustration or disdain towards individuals who exhibit such behavior.