Lethargic /lə-ˈthär-jik/ adj. 

Definition: Lethargic refers to someone who is experiencing lethargy or a feeling of laziness and a lack of energy. This word can be used to describe a person in general but is also often used in the medical community as a symptom of sickness. Secondarily, it can also refer to someone being apathetic towards something.

Etymology: The first use of this word in print in English dates back to the 1590s. Lethargic comes from the Greek lethe, meaning forgetfulness. In Greek mythology, a river by the name of Lethe ran through the underworld. When someone died, their soul was given a drink from this “River of Forgetfulness” to forget the details of their life. In forgetting, the souls often felt sluggish and indifferent after this, which is where the connection between the word and the feelings came.

In a Sentence

After she got out of the hospital, she was still feeling lethargic for several days.

The board was lethargic in coming to a decision about the after-school program proposal.

After the Thanksgiving meal, the entire family sat around the table, too lethargic to even speak.

Synonyms 

Sluggish, Inactive, Apathetic

Antonyms 

Active, Energetic, Animated