The Collaborative International Dictionary of English v.0.48:

complaining \complaining\ (k[o^]m*pl[=a]n"[i^]mg) adj.
   uttering complaints. Opposite of uncomplaining.
   [prenominal]

   Note: [Narrower terms: faultfinding, grumbling(prenominal):
         fretful, querulous, whiney, whining(prenominal),
         whiny; protesting(prenominal), protestant]

   Syn: complaintive.
        [WordNet 1.5]