Evasion: A mental process of willfully suppressing your knowledge of the world.
Evasion is the means by which a person is irrational. Irrationality is more than just ignorance. It's willfully ignoring information you have. To ignore it, you have to divert your mind from it. That means either focusing on something else, or trying not to focus on those facts. Evasion is the process of trying to ignore something.
Evasion is like changing the topic of a conversation that you're afraid to have. You look away from the knowledge, and try to ignore it. There may be many motivations for evasion. You may feel uncomfortable thinking about a topic, or you may think that certain ideas are evil. Or you might think that the information doesn't reflect too kindly on you, and so you don't want to think about it.