Akrasia [ἀκρασία] is often translated as incontinence. It is the phenomenon which in ordinary language is usually referred to as weakness of will. Akrasia is said to be a deficiency of character. An akratic person usually has a good grasp of what is good and has the right kinds of ends in mind. The akratic may even give one or two good moral advices to those who are in need of advice, but she ultimately doesn’t see the main point and often acts against her better judgement. Someone suffering from akrasia possesses the ability of good reasoning, but she yields to temptation and doesn’t proceed according to her good reasoning. She is usually under severe influence of her impulses and passions [πάθος] . An akratic person, according to Richard Kraut, “experiences passions that conflict with his rational choice [and] that gives in to feeling rather than reason more often than the average person”. (1) The akratic shouldn’t be confused with a self-indulgent person. Although the self-indulgent and the akratic are both wrong when it comes to pleasure, they are wrong in different ways. The akratic agent is mainly weak, however the self-indulgent is generally considered as a type of bad person.
(1) Richard Kraut, "Aristotle's Ethics", The Stanford Encyclopedia of Philosophy.