To put or categorize someone or something in the same manner or group as someone or something else, especially in a careless, hasty, or indiscriminately. Just because I've dabbled in drugs and alcohol doesn't mean I deserve to be lumped in with those degenerates. Kids, please don't lump the dark clothes with the whites—they need to be separated before they go in the washing machine! We've still got room in our car, if you want to lump your bags in with ours.