Source : Webster's Revised Unabridged Dictionary (1913)

Lifeless \Life"less\, a.
   Destitute of life, or deprived of life; not containing, or
   inhabited by, living beings or vegetation; dead, or
   apparently dead; spiritless; powerless; dull; as, a lifeless
   carcass; lifeless matter; a lifeless desert; a lifeless wine;
   a lifeless story. -- {Life"less*ly}, adv. --
   {Life"less*ness}, n.

   Syn: Dead; soulless; inanimate; torpid; inert; inactive;
        dull; heavy; unanimated; spiritless; frigid; pointless;
        vapid; flat; tasteless.

   Usage: {Lifeless}, {Dull}, {Inanimate}, {Dead}. In a moral
          sense, lifeless denotes a want of vital energy;
          inanimate, a want of expression as to any feeling that
          may be possessed; dull implies a torpor of soul which
          checks all mental activity; dead supposes a
          destitution of feeling. A person is said to be
          lifeless who has lost the spirits which he once had;
          he is said to be inanimate when he is naturally
          wanting in spirits; one is dull from an original
          deficiency of mental power; he who is dead to moral
          sentiment is wholly bereft of the highest attribute of
          his nature.

Source : WordNet®

lifelessness
     n : not having life [syn: {inanimateness}] [ant: {animateness}]