The performance of "virtuous actions with uncommon promptitude, ease, and pleasure, from supernatural motives and without human reasoning, with self-abnegation and full control over natural inclinations."
It is so defined by Benedict XIV in his treatise on beatification and canonization.
It means eminence in practise of the social or cardinal virtues, prudence, justice, temperance, and fortitude, and in the theological or godly virtues, faith, hope, and charity.
The principal requirement in the process for the beatification and canonization is to prove that a servant of God practised these virtues in an extraordinary or heroic manner.
New Catholic Dictionary