Lassitude is defined as a feeling of lethargy or a lack of mental or physical energy.(noun)
When you are in a state where you don't want to do anything except lay around, this is an example of lassitude.
See lassitude in Webster's New World College Dictionary
Origin: Fr < L lassitudo < lassus, faint, weary: see late
See lassitude in American Heritage Dictionary 4
Origin: Middle English
Origin: , from Old French
Origin: , from Latin lassitūdō
Origin: , from lassus, weary; see lē- in Indo-European roots.
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