lethargic
le-thar-gic
adjective
Feeling or showing a lack of energy, enthusiasm, or interest; sluggish.
"The heat made him feel lethargic all day."
Thesaurus
Synonyms: lackadaisical, unenergetic, stuporous, listless, groggy, foggy, logy, languorous, languid, dazed, dreamy
Antonyms: energetic