Nastiness/ˈnæstinəs/ Definition 1 of 3Pro Tip 1/2Negative Emotion Used to describe actions or words that are hurtful and create a bad feeling. His nastiness left everyone in the room feeling uncomfortable. Pro Tip 2/2Unpleasant Attitudes Can refer to a person's character when they are frequently unpleasant or cruel. His constant nastiness made him unpopular among his peers.