How does one define 'lethargic'?

The term 'lethargic' is defined as being deficient in alertness or activity. When someone is described as lethargic, it indicates a state of sluggishness or a lack of energy, which often results in decreased responsiveness or a general feeling of drowsiness. This word is commonly used to describe a person who is feeling unusually tired or inactive, making it necessary to identify a contrasting state to fully grasp its meaning.

In contrast, the other choices describe the opposite qualities of energy and responsiveness. The first choice implies an excess of energy, which directly contradicts lethargy. The third option emphasizes extreme enthusiasm, which also runs counter to the idea of being lethargic. The fourth choice speaks to a high level of responsiveness, which again is not in alignment with the reduced alertness and activity associated with lethargy. Therefore, the correct choice captures the essence of lethargy accurately.