The Collaborative International Dictionary of English v.0.48:

Whiner \Whin"er\, n.
   One who, or that which, whines.
   [1913 Webster]

WordNet (r) 3.0 (2006):

whiner
    n 1: a person given to excessive complaints and crying and
         whining [syn: whiner, complainer, moaner,
         sniveller, crybaby, bellyacher, grumbler,
         squawker]