1. a loss of physical balance, as in Parkinson’s disease and ataxias due to cerebellar disorder or injury.

2. emotional imbalance, as in individuals with extreme mood swings (labile affect).

3. in developmental psychology, a state of tension between cognitive processes competing against each other. In contrast to Jean Piaget, some theorists believe that disequilibrium is the optimal state for significant cognitive advances to occur. See also equilibration.