The Collaborative International Dictionary of English v.0.48:

droopy \droopy\ adj.
   bending downward due to lack of tautness; -- of lines.

   Syn: drooping, sagging, slack.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

droopy
    adj 1: hanging down (as from exhaustion or weakness) [syn:
           drooping, droopy, sagging]

Moby Thesaurus II by Grady Ward, 1.0:

155 Moby Thesaurus words for "droopy":
   anemic, apathetic, asthenic, bagging, baggy, ballooning, benumbed,
   blase, bloodless, bored, bowed-down, cast down, chicken, cowardly,
   dashed, dead, debilitated, dejected, depressed, despairing,
   despondent, desponding, discouraged, disheartened, dispirited,
   dopey, dormant, down, downcast, downhearted, drooping, drugged,
   dull, effete, enervated, enfeebled, etiolated, exanimate, fagged,
   faint, fainting, faintish, fatigued, feeble, feeling faint,
   feeling low, flabby, flaccid, flagging, floppy, footsore, frazzled,
   gone, good and tired, gutless, heartless, heavy, hebetudinous,
   hypochondriac, hypochondriacal, imbecile, impotent, in low spirits,
   in the depths, in the doldrums, in the dumps, inanimate, inert,
   jaded, lackadaisical, languid, languishing, languorous, leaden,
   lethargic, lifeless, limber, limp, listless, loose, lop, lop-eared,
   loppy, low, low-spirited, lumpish, lustless, marrowless, moribund,
   nerveless, nodding, numb, pessimistic, phlegmatic, pining,
   pithless, pooped, powerless, ready to drop, rubbery, run ragged,
   run-down, sagging, sagging in folds, saggy, sapless, sated, seedy,
   sinewless, slack, sleepy, slow, sluggish, soft, somnolent,
   spineless, spiritless, stagnant, stagnating, strengthless,
   stultified, subdued, suicidal, supine, swag, tired, tired-winged,
   toilworn, torpid, unhardened, unnerved, unrefreshed, unrestored,
   unstrung, vegetable, vegetative, wan, way-weary, wayworn, weak,
   weakened, weakly, wearied, weariful, weary, weary of life,
   weary-footed, weary-laden, weary-winged, weary-worn, wilting,
   woebegone, world-weary, worn, worn-down