Is your pet slug always this comatose, or is this display of lethargy unusual? The word lethargy describes inactivity or a lack of energy.
Lethargy comes from the Greek lethargos, originally meaning “inactive through forgetfulness.” Somewhere along the way, the word lost the implication of “forgetfulness” and just ended up hanging around in bed all day. Still, lethargy doesn’t necessarily imply laziness; it can be brought about by illness and may also describe a lack of strength. Other lethargic nouns include torpor, sluggishness, and languor.