Source : Webster's Revised Unabridged Dictionary (1913)

Listless \List"less\, a. [OE. listles, lustles. See {Lust}.]
   Having no desire or inclination; indifferent; heedless;
   spiritless. `` A listless unconcern.'' --Thomson.

         Benumbed with cold, and listless of their gain.
                                                  --Dryden.

         I was listless, and desponding.          --Swift.

   Syn: Heedless; careless; indifferent; vacant; uninterested;
        languid; spiritless; supine; indolent. --
        {List"less*ly}, adv. -- {List"less*ness}, n.

Source : WordNet®

listlessly
     adv : in a listless manner; "they shook hands rather listlessly"