The Collaborative International Dictionary of English v.0.48:

nymph \nymph\ (n[i^]mf), n. [L. nympha nymph, bride, young
   woman, Gr. ny`mfh: cf. F. nymphe. Cf. Nuptial.]
   [1913 Webster]
   1. (Class. Myth.) A goddess of the mountains, forests,
      meadows, or waters.
      [1913 Webster]

            Where were ye, nymphs, when the remorseless deep
            Closed o'er the head of your loved Lycidas?
                                                  --Milton.
      [1913 Webster]

   2. Hence: A lovely young girl; a maiden; a damsel.
      [1913 Webster]

            Nymph, in thy orisons
            Be all my sins remembered.            --Shak.
      [1913 Webster]

   3. (Zool.) The pupa of an insect; a chrysalis.
      [1913 Webster]

   4. (Zool.) Any one of a subfamily (Najades) of butterflies
      including the purples, the fritillaries, the peacock
      butterfly, etc.; -- called also naiad.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nymph
    n 1: (classical mythology) a minor nature goddess usually
         depicted as a beautiful maiden; "the ancient Greeks
         believed that nymphs inhabited forests and bodies of water"
    2: a larva of an insect with incomplete metamorphosis (as the
       dragonfly or mayfly)
    3: a voluptuously beautiful young woman [syn: nymph, houri]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "nymph":
   Anlage, Atlantides, Hyades, Napaea, Pleiades, arachnid, arthropod,
   aurelia, beetle, blastula, bug, caterpillar, centipede, chilopod,
   chippy, chrysalis, cocoon, daddy longlegs, diplopod, dryad, embryo,
   fetus, floozy, flower nymph, fly, germ, germen, glen nymph,
   grisette, grub, hamadryad, harvestman, hexapod, insect, larva,
   limoniad, maggot, millepede, millipede, mite, mountain nymph,
   nympha, nymphet, nymphlin, oread, pupa, rudiment, scorpion, spider,
   tarantula, tick, tree nymph, vila, wiggler, willi, wood nymph,
   wriggler, zygote