[syn: inactiveness, inactivity, inertia]
3.  being inactive;  being less active; 
The Collaborative International Dictionary of English v.0.48:
Inactivity \In`ac*tiv"i*ty\, n. [Cf. F. inactivit['e].]
   [1913 Webster]
   1. The state or quality of being inactive; inertness; as, the
      inactivity of matter.
      [1913 Webster]
   2. Idleness; habitual indisposition to action or exertion;
      lack of energy; sluggishness.
      [1913 Webster]
            The gloomy inactivity of despair.     --Cook.
      [1913 Webster]
WordNet (r) 3.0 (2006):
inactivity
    n 1: the state of being inactive [syn: inaction, inactivity,
         inactiveness] [ant: action, activeness, activity]
    2: a disposition to remain inactive or inert; "he had to
       overcome his inertia and get back to work" [syn:
       inactiveness, inactivity, inertia] [ant: activeness,
       activity]
    3: being inactive; being less active [ant: activity]
Moby Thesaurus II by Grady Ward, 1.0:
84 Moby Thesaurus words for "inactivity":
   a wise passiveness, comfort, contemplation, contemplative life,
   deliberateness, deliberation, do-nothing policy, do-nothingism,
   do-nothingness, dolce far niente, dormancy, ease, fixation, fixity,
   hastelessness, hibernation, idleness, immobility, inaction,
   inactiveness, indolence, inertia, inertness, laissez-aller,
   laissez-faire, laissez-faireism, languidness, laziness,
   leisureliness, lethargy, lifelessness, listlessness, meditation,
   motionlessness, neutralism, neutrality, neutralness,
   noninvolvement, nonparticipation, nonresistance, nonviolence,
   nonviolent resistance, pacifism, paralysis, passive resistance,
   passive self-annihilation, passiveness, passivism, passivity,
   peace, peacefulness, placidity, placidness, policy,
   procrastination, quiescence, quiet, quietism, relaxation,
   relaxedness, repose, rest, restfulness, serenity, sleep, sloth,
   slothfulness, slowness, sluggishness, somnolence, stagnancy,
   stagnation, standpattism, stasis, stillness, torpor, tranquillity,
   unbuttoned ease, unhastiness, unhurriedness, vegetation,
   vita contemplativa, waiting game, watching and waiting