sluggishness

noun

1. A deficiency in mental and physical alertness and activity: dullness, hebetude, languidness, languor, lassitude, leadenness, lethargy, listlessness, stupor, torpidity, torpor. See action/inaction.
2. The quality or state of being lazy: idleness, indolence, laziness, shiftlessness, sloth, slothfulness, sluggardness. Informal do-nothingism. See industrious/lazy.

Definition: lack of activity
Antonyms: briskness

The noun has 2 meanings:

Meaning #1: a state of comatose torpor (as found in sleeping sickness)
  Synonyms: lethargy, lassitude

Meaning #2: inactivity; showing an unusual lack of energy
  Synonyms: languor, lethargy, phlegm