Source : Webster's Revised Unabridged Dictionary (1913)

Inactivity \In`ac*tiv"i*ty\, n. [Cf. F. inactivit['e].]
   1. The state or quality of being inactive; inertness; as, the
      inactivity of matter.

   2. Idleness; habitual indisposition to action or exertion;
      want of energy; sluggishness.

            The gloomy inactivity of despair.     --Cook.

Source : WordNet®

inactivity
     n 1: the state of being inactive [syn: {inaction}, {inactiveness}]
          [ant: {action}, {action}, {action}]
     2: a disposition to remain inactive or inert; "he had to
        overcome his inertia and get back to work" [syn: {inactiveness},
         {inertia}] [ant: {activeness}]
     3: being inactive; being less active [ant: {activity}]