Drawing inspiration from Pseudo-Dionysius, Maximus the Confessor, and Thomas Aquinas, and in support of the definition of evil as the privation of being or goodness, this article proposes a complementary definition of evil. It argues that evil can be defined as the non-advancement of being, appetite, or natural inclination toward its proper perfection or completion. First, it explains what this definition entails, elaborates on its implications, and defends its plausibility. Second, it discusses typical objections to the privation account and shows how defining evil relative to appetite can help overcome them.