Bright-eyed and bushy-tailed is an idiom used to describe someone who is alert, enthusiastic, and full of energy. The opposite of this phrase would be someone who is tired, unenthusiastic, and lacking energy. Some antonyms for this phrase could include terms such as lethargic, sluggish, and apathetic. These terms describe someone who is lacking energy, motivation, or interest. Another antonym could be somber, indicating someone who is serious or sad, lacking the lighthearted and enthusiastic energy that the original phrase connotes. Overall, antonyms for bright-eyed and bushy-tailed describe a lack of energy and enthusiasm, the exact opposite of someone who is thriving and lively.