Slumbering typically refers to being asleep or in a state of rest, and its antonyms are words that describe activity, wakefulness, or alertness. Some opposite words for more slumbering are bustling, active, alert, lively, awake, and animated. These words suggest a state of being energetic, lively, or completely awake instead of feeling sleepy or drowsy. When we want to describe a person or thing that is not slumbering and is very active, we use these antonyms. For example, a bustling city, a lively dance floor, an alert guard, an active bee, an awake student, and an animated cartoon character.