The Collaborative International Dictionary of English v.0.48:

Querulous \Quer"u*lous\, a. [L. querulus and querulosus, fr.
   queri to complain. Cf. Cry, v., Quarrel a brawl,
   Quarrelous.]
   1. Given to quarreling; quarrelsome. [Obs.] --land.
      [1913 Webster]

   2. Apt to find fault; habitually complaining; disposed to
      murmur; as, a querulous man or people.
      [1913 Webster]

            Enmity can hardly be more annoying that querulous,
            jealous, exacting fondness.           --Macaulay.
      [1913 Webster]

   3. Expressing complaint; fretful; whining; as, a querulous
      tone of voice.
      [1913 Webster]

   Syn: Complaining; bewailing; lamenting; whining; mourning;
        murmuring; discontented; dissatisfied.
        [1913 Webster] -- Quer"u*lous*ly, adv. --
        Quer"u*lous*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

querulous
    adj 1: habitually complaining; "a whiny child" [syn: fretful,
           querulous, whiney, whiny]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "querulous":
   Jeremianic, annoyed, bad-tempered, beefing, bellyaching, bemoaning,
   bitching, blubbering, cantankerous, carping, catty, censorious,
   choleric, complaining, complaintful, crabbing, crabby, cranky,
   critical, criticizing, croaking, cross, crotchety, crusty, crying,
   disappointed, discontented, disgruntled, displeased, dissatisfied,
   dyspeptic, envious, faultfinding, finical, finicky, fractious,
   fretful, fussy, griping, grouchy, grousing, growling, grumbling,
   grumpy, howling, huffy, hypercritical, ill-humored, ill-natured,
   ill-tempered, irascible, irritable, irritated, lamenting,
   lamentive, malcontent, malcontented, moanful, mournful, murmuring,
   muttering, nagging, naggy, out of humor, peevish, perverse,
   pettish, petulant, piqued, plaintive, plangent, puling,
   quarrelsome, querulant, rebellious, resentful, restive, restless,
   shrewish, snappish, sorrowful, sour, splenetic, sulky, testy,
   touchy, ululant, unaccepting, unaccommodating, uneasy, unfulfilled,
   ungratified, unhappy, unsatisfied, vixenish, vixenly, wailful,
   wailing, waspish, weeping, whimpering, whining, whiny