WordNet (r) 3.0 (2006):

kvetch
    n 1: (Yiddish) a constant complainer
    2: (Yiddish) a nagging complaint
    v 1: express complaints, discontent, displeasure, or
         unhappiness; "My mother complains all day"; "She has a lot
         to kick about" [syn: complain, kick, plain, sound
         off, quetch, kvetch] [ant: cheer, cheer up, chirk
         up]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "kvetch":
   bellyacher, complainant, complainer, crab, crank, croaker,
   faultfinder, frondeur, griper, grouch, grouser, growler, grumbler,
   kicker, malcontent, murmurer, mutterer, querulous person,
   reactionary, reactionist, rebel, sorehead, whiner