Source : Webster's Revised Unabridged Dictionary (1913)

Sluggish \Slug"gish\, a.
   1. Habitually idle and lazy; slothful; dull; inactive; as, a
      sluggish man.

   2. Slow; having little motion; as, a sluggish stream.

   3. Having no power to move one's self or itself; inert.

            Matter, being impotent, sluggish, and inactive, hath
            no power to stir or move itself.      --Woodward.

            And the sluggish land slumbers in utter neglect.
                                                  --Longfellow.

   4. Characteristic of a sluggard; dull; stupid; tame; simple.
      [R.] ``So sluggish a conceit.'' --Milton.

   Syn: Inert; idle; lazy; slothful; indolent; dronish; slow;
        dull; drowsy; inactive. See {Inert}. -- {Slug"gish*ly},
        adv. -- {Slug"gish*ness}, n.

Source : WordNet®

sluggishness
     n 1: a state of comatose torpor (as found in sleeping sickness)
          [syn: {lethargy}, {lassitude}]
     2: inactivity; showing an unusual lack of energy [syn: {languor},
         {lethargy}, {phlegm}]