"lassitude" in the noun sense
1. lethargy, lassitude, sluggishness
a state of comatose torpor (as found in sleeping sickness)
2. languor, lassitude, listlessness
a feeling of lack of interest or energy
3. inanition, lassitude, lethargy, slackness
weakness characterized by a lack of vitality or energy
Source: WordNet® (An amazing lexical database of English)
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