The Collaborative International Dictionary of English v.0.48:

Spiritless \Spir"it*less\, a.
   1. Destitute of spirit; wanting animation; wanting
      cheerfulness; dejected; depressed.
      [1913 Webster]

   2. Destitute of vigor; wanting life, courage, or fire.
      [1913 Webster]

            A men so faint, so spiritless,
            So dull, so dead in lock, so woebegone. --Shak.
      [1913 Webster]

   3. Having no breath; extinct; dead. "The spiritless body."
      --Greenhill.
      [1913 Webster] -- Spir"it*less*ly, adv. --
      Spir"it*less*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spiritless
    adj 1: lacking ardor or vigor or energy; "a spiritless reply to
           criticism" [ant: spirited]
    2: evidencing little spirit or courage; overly submissive or
       compliant; "compliant and anxious to suit his opinions of
       those of others"; "a fine fiery blast against meek
       conformity"- Orville Prescott; "she looked meek but had the
       heart of a lion"; "was submissive and subservient" [syn:
       meek, spiritless]