Some antonyms for the word "in a lively manner" include "sluggishly," "lethargically," "dull," "lifelessly," and "dejectedly." These words all suggest a lack of energy, enthusiasm or vitality. Instead of being lively and animated, a person or situation described with these antonyms might appear slow, lazy, or uninterested. In contrast, when someone is lively, they are often characterized as being engaged, joyous, and spirited. Using antonyms like these can help to provide a sense of contrast and nuance to a piece of writing, giving the reader a more vivid understanding of the mood, tone, and emotions involved.