The Collaborative International Dictionary of English v.0.48:

Puppy \Pup"py\, n.; pl. Puppies. [F. poup['e]e doll, puppet.
   See Puppet, and cf. Pup, n.]
   1. (Zool.) The young of a canine animal, esp. of the common
      dog; a whelp.
      [1913 Webster]

   2. A name of contemptuous reproach for a conceited and
      impertinent person.
      [1913 Webster]

            I found my place taken by an ill-bred, awkward puppy
            with a money bag under each arm.      --Addison.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Puppy \Pup"py\, v. i. [imp. & p. p. Puppied; p. pr. & vb. n.
   Puppying.]
   To bring forth whelps; to pup.
   [1913 Webster]

WordNet (r) 3.0 (2006):

puppy
    n 1: a young dog
    2: an inexperienced young person [syn: puppy, pup]

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "puppy":
   Beau Brummel, Seeing Eye dog, bandog, beau, birdling, bitch, blade,
   blood, boldface, boulevardier, bowwow, boy, brazenface, bub, bubba,
   buck, bud, buddy, calf, canine, catling, chick, chickling, chicky,
   chutzpanik, clotheshorse, colt, coxcomb, cub, dandy, dog, dogie,
   duckling, dude, exquisite, fancy dog, fashion plate, fawn, fellow,
   fine gentleman, fledgling, foal, fop, fribble, fryer, gallant,
   gosling, guide dog, gyp, hobbledehoy, hussy, jack-a-dandy,
   jackanapes, kennel, kid, kit, kitten, lad, laddie, lady-killer,
   lamb, lambkin, lap dog, litter, macaroni, malapert, man-about-town,
   manchild, masher, master, minx, muchacho, nest, nestling,
   pack of dogs, piglet, pigling, polliwog, pooch, pullet, pup,
   saucebox, schoolboy, sheep dog, shoat, show dog, sled dog, slut,
   smart aleck, smart-ass, smarty, smarty-pants, sonny, sonny boy,
   spark, sport, sprat, squirt, squit, swaggerer, swell, tadpole,
   toy dog, upstart, watchdog, weaner, whelp, whippersnapper,
   wise guy, wise-ass, working dog, yeanling, young man, youth