The rudeness in his answer made everyone in the room feel awkward.

rudeness 是由形容词 rude（粗鲁的、无礼的）加上名词后缀 -ness 构成的名词，表示"粗鲁无礼的状态或性质"。后缀 -ness 通常用于将形容词转化为抽象名词，表示某种性质或状态。