Definition of lethargic:
deficient in alertness or activity
Synonyms of lethargic:
unenergetic, sluggish, listless, lazy, inactive, torpid, slow, sleepy, slothful, apathetic
Opposite/Antonyms of lethargic:
energetic, active, busy, lively, perky, alert, vivacious, vigorous, vital, animated
Sentence/Example of lethargic:
If the cat is lethargic and his coat is dull and unhealthy looking, this too may be a sign.