废话：不用说大家都知道的事情，说出来就是废话 胡说：说的话和事实不相符，就是胡说

to state obvious and to speak something nonsense is different

废话是胡说的结果 哈哈哈 if u say something without thinking ,for no reasons and no logic...that what u said is no meaning and unuseful...... by the way 胡说 is a verb and 废话 is a none ...

"废话"比较无礼貌仅限于关系好的朋友means：Geez: hi萨妮亚,are you a human? 萨妮亚:废话 "胡说"means：that's not right

废话 means useless words, everybody knows or not helpful. 胡说 means saying something not true or not realistic.