Cyclothymic disorder refers to chronic mood disorder (at least 2 years) characterized by alternating mood elevation and depression levels that are not as severe as manic or major depressive episodes .
Other /More definition:
Cyclothymic disorder refers to milder but more chronic form of Bipolar disorder that consists of alternation between hypomanic episodes and mild depressive episodes over a period of at least two years. Moderate manic and depressive behavior that persists for 2 years or more; a chronic (at least 2 years) mood disorder characterized by alternating mood elevation and depression levels that are not as severe as manic or major depressive episodes. Moreover, Cyclothymic disorder is a mood disorder that, compared with Bipolar disorder, involves a less intense vacillation between states of Euphoria and Dysphoria.