Torpor
Etymology
From Latin torpor, "numbness, sluggishness," from torpere, "to be numb or stiff" (a relative of "torpedo," originally the electric ray that numbs its prey). The word joins two ideas: lack of feeling and lack of motion. Zoology uses it for the reduced metabolic state some animals enter to conserve energy, a lighter cousin of hibernation.
noun · /TOR-por/
A state of sluggish inactivity, physical or mental dullness, and lowered energy.
What it names
The heavy, slowed-down condition of a body or mind that has lost its vigor — drowsy, numb, and reluctant to move, whether from cold, illness, or listlessness.
Example
The afternoon heat sank the whole office into a torpor, keyboards clacking at half their usual speed.
Related idea
Lethargy names much the same drowsy sluggishness but with a stronger sense of weariness; torpor leans harder on numbness and near-suspended function, as in an animal’s winter slowdown.