The previous answer seems about right. "Absolutely" implies that there are no exceptions: An absolutely clear explanation is one that can be understood perfectly. An absolutely perfect day is a day in which everything went perfectly. You'd never revert to a "definitely clear explanation" or a "definitely perfect day." "Definitely" implies certainty: "I will definitely study Japanese more" means that I'm sure I'm going to do it. "I definitely think that A is better than B" means that I'm sure that A is better than B.

Definitely means "without any doubt " Absolutely means " completely (to be greatest degree possible) and in any way"