lethargic
Definitions
Affected by lethargy; sluggish and apathetic.
Characterized by a lack of energy and enthusiasm.
Examples
After the heavy Thanksgiving meal, I felt too lethargic to do anything but nap on the couch.
The hot summer sun made the stray cat feel lethargic as it lounged in the shade.
A lack of sleep left the students feeling lethargic and unable to focus during the morning lecture.