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]