definitions from the web:
1. to declare or affirm solemnly and formally as true
2. Positive statements that are repeated with a goal of reprogramming the mind and its belief systems.
3. Daily messages accompanied by visualizations of a positive outcome, that are said to oneself to bring about a change within the inner self.
5. Saying certain phrases over and over again in a positive way to help you achieve your goals. Similar to meditation or prayer.