The Collaborative International Dictionary of English v.0.48:

Languid \Lan"guid\, a. [L. languidus, fr. languere to be faint
   or languid: cf. F. languide. See Languish.]
   [1913 Webster]
   1. Drooping or flagging from exhaustion; indisposed to
      exertion; without animation; weak; weary; heavy; dull. "
      Languid, powerless limbs. " --Armstrong.
      [1913 Webster]

            Fire their languid souls with Cato's virtue.
                                                  --Addison.
      [1913 Webster]

   2. Slow in progress; tardy. " No motion so swift or languid."
      --Bentley.
      [1913 Webster]

   3. Promoting or indicating weakness or heaviness; as, a
      languid day.
      [1913 Webster]

            Feebly she laugheth in the languid moon. --Keats.
      [1913 Webster]

            Their idleness, aimless flirtations and languid
            airs.                                 --W. Black.

   Syn: Feeble; weak; faint; sickly; pining; exhausted; weary;
        listless; heavy; dull; heartless. -- Lan"guid*ly, adv.
        -- Lan"guid*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

languid
    adj 1: lacking spirit or liveliness; "a lackadaisical attempt";
           "a languid mood"; "a languid wave of the hand"; "a hot
           languorous afternoon" [syn: dreamy, lackadaisical,
           languid, languorous]

Moby Thesaurus II by Grady Ward, 1.0:

247 Moby Thesaurus words for "languid":
   Laodicean, Olympian, abeyant, aloof, ambling, anemic, anesthetized,
   apathetic, asthenic, benumbed, blah, blase, bloodless, bored,
   cataleptic, catatonic, cautious, chicken, circumspect, claudicant,
   comatose, cowardly, crawling, creeping, creeping like snail, dead,
   debilitated, deliberate, desensitized, detached, disinterested,
   doped, dopey, dormant, dozy, dreamy, drooping, droopy, drowsy,
   drugged, drugged with sleep, dull, easy, effete, enervated,
   enfeebled, etiolated, exanimate, fagged, faint, fainting, faintish,
   faltering, fatigued, feeble, feeling faint, flabby, flaccid,
   flagging, flat, floppy, foot-dragging, footsore, foul, frazzled,
   gentle, gone, good and tired, gradual, groggy, gutless,
   half asleep, halting, heartless, heavy, heavy with sleep,
   heavy-eyed, hebetudinous, hobbled, hobbling, hopeless, idle,
   imbecile, impassive, impotent, in a stupor, in abeyance,
   in suspense, inactive, inanimate, indifferent, indolent, inert,
   insouciant, jaded, lackadaisical, languishing, languorous, latent,
   lazy, leaden, leisurely, lethargic, lifeless, limber, limp,
   limping, listless, logy, lumbering, lumpish, lustless, marrowless,
   moderate, moribund, napping, narcoleptic, narcose, narcotized,
   narcous, nerveless, nodding, nonchalant, numb, numbed, oscitant,
   out of it, passive, phlegmatic, pithless, pluckless, poking, poky,
   pooped, powerless, ready to drop, relaxed, reluctant, resigned,
   rubbery, run ragged, run-down, sagging, sapless, sated, sauntering,
   sedated, sedentary, seedy, shuffling, sinewless, slack,
   sleep-drowned, sleep-drunk, sleep-filled, sleep-swollen, sleepful,
   sleeping, sleepy, slothful, slow, slow as death, slow as molasses,
   slow as slow, slow-crawling, slow-foot, slow-going, slow-legged,
   slow-moving, slow-paced, slow-poky, slow-running, slow-sailing,
   slow-stepped, sluggish, slumbering, slumberous, slumbery,
   smoldering, snail-paced, snaillike, snoozy, soft, somnolent,
   soporific, spineless, spiritless, spunkless, staggering, stagnant,
   stagnating, standing, static, stoic, strengthless, stretchy,
   strolling, stultified, stupefied, stuporose, stuporous, supine,
   suspended, tame, tentative, tired, tired-winged, toddling,
   toilworn, torpid, tortoiselike, tottering, trudging, turtlelike,
   unaroused, uncaring, unconcerned, unhardened, unhurried,
   uninterested, unnerved, unrefreshed, unrestored, unstrung,
   vegetable, vegetative, waddling, wan, way-weary, wayworn, weak,
   weakened, weakly, wearied, weariful, weary, weary-footed,
   weary-laden, weary-winged, weary-worn, wilting, withdrawn,
   world-weary, worn, worn-down, yawning, yawny