The Collaborative International Dictionary of English v.0.48:

ambrosia \am*bro"sia\ ([a^]m*br[=o]"zh[.a]
   or[a^]m*br[=o]"zh[i^]*[.a]; 277), n. [L. ambrosia, Gr.
   'ambrosi`a, properly fem. of 'ambro`sios, fr. 'a`mbrotos
   immortal, divine; 'a priv. + broto`s mortal (because it was
   supposed to confer immortality on those who partook of it).
   broto`s stands for mroto`s, akin to Skr. m[.r]ita, L.
   mortuus, dead, and to E. mortal.]
   1. (Myth.)
      (a) The fabled food of the gods (as nectar was their
          drink), which conferred immortality upon those who
          partook of it.
      (b) An unguent of the gods.
          [1913 Webster]

                His dewy locks distilled ambrosia. --Milton.
          [1913 Webster]

   2. A perfumed unguent, salve, or draught; something very
      pleasing to the taste or smell. --Spenser.
      [1913 Webster]

   3. Formerly, a kind of fragrant plant; now (Bot.), a genus of
      plants, including some coarse and worthless weeds, called
      ragweed, hogweed, etc.
      [1913 Webster]

   4. (Zool.) The food of certain small bark beetles, family
      Scolytidae believed to be fungi cultivated by the
      beetles in their burrows.
      [Webster 1913 Suppl.]

   5. A dessert made from shredded coconuts and oranges,
      sometimes including other ingredients such as marshmallow.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

ambrosia
    n 1: a mixture of nectar and pollen prepared by worker bees and
         fed to larvae [syn: beebread, ambrosia]
    2: any of numerous chiefly North American weedy plants
       constituting the genus Ambrosia that produce highly
       allergenic pollen responsible for much hay fever and asthma
       [syn: ragweed, ambrosia, bitterweed]
    3: fruit dessert made of oranges and bananas with shredded
       coconut
    4: (classical mythology) the food and drink of the gods; mortals
       who ate it became immortal [syn: ambrosia, nectar]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "ambrosia":
   Caesar salad, Jell-O salad, Waldorf salad, ambergris, aromatic,
   aromatic gum, aromatic water, artificial sweetener, aspic, attar,
   attar of roses, balm, balm of Gilead, balsam, bay oil,
   bergamot oil, blackstrap, bonne bouche, calcium cyclamate,
   cane syrup, cate, champaca oil, chef salad, choice morsel, civet,
   clover honey, cole slaw, comb honey, combination salad, corn syrup,
   crab Louis, cyclamates, dainty, delicacy, dessert, edulcoration,
   essence, essential oil, extract, fixative, fruit salad, goody,
   green salad, heliotrope, herring salad, honey, honeycomb, honeydew,
   honeypot, jasmine oil, kickshaw, lavender oil, macaroni salad,
   manna, maple syrup, molasses, morsel, musk, myrcia oil, myrrh,
   nectar, parfum, perfume, perfumery, potato salad, rose oil,
   saccharification, saccharin, salad, salade, salmagundi, savory,
   scent, slaw, sodium cyclamate, sorghum, sugar, sugar-making,
   sugaring off, sweetener, sweetening, sweets, syrup, tidbit, titbit,
   tossed salad, treacle, treat, volatile oil