To spite is to intentionally annoy, hurt, or upset even when there might be no (apparent) gain, and even when those actions might cause the person spiting harm, as well. Spiteful words or actions are delivered in such a way that it is clear that the person is delivering them just to annoy, hurt, or upset. When the intent to annoy, hurt, or upset is shown subtly, behavior is considered catty.
In his 1929 examination of emotional disturbances, Psychology and Morals: An Analysis of Character, J. A. Hadfield uses deliberately spiteful acts to illustrate the difference between disposition and sentiment.
The Underground Man, in Fyodor Dostoevsky's novella Notes from Underground, is an example of spite. His motivation remains constantly spiteful, undercutting his own existence and ability to live.