WordNet (r) 3.0 (2006):

smart aleck
    n 1: an upstart who makes conceited, sardonic, insolent comments
         [syn: wise guy, smart aleck, wiseacre, wisenheimer,
         weisenheimer]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "smart aleck":
   Narcissus, blowhard, boaster, boldface, braggadocio, braggart,
   brazenface, chutzpanik, egocentric, egoist, egotist, exhibitionist,
   gasbag, grandstander, hot-air artist, hussy, individualist,
   know-it-all, malapert, minx, narcissist, narcist, no modest violet,
   pup, puppy, saucebox, show-off, smart-ass, smarty, smarty-pants,
   swaggerer, swellhead, upstart, whippersnapper, windbag, wise guy,
   wise-ass, wiseacre, wisecracker, wisehead, wisenheimer