Slack off Definition 1 of 2Pro Tip 1/3Informal Usage Used in casual conversations, not in formal or professional settings. I need to stop slacking off and finish my project. Pro Tip 2/3Negative Connotation Implies a lack of responsibility or commitment, often seen unfavorably. She got fired for slacking off too often at work. Pro Tip 3/3Not Always Laziness Can indicate taking a necessary rest or break without being lazy. After studying intensely, he's slacking off for a day.