The Collaborative International Dictionary of English v.0.48:

Vegetable \Veg`e*ta*ble\, a. [F. v['e]g['e]table growing,
   capable of growing, formerly also, as a noun, a vegetable,
   from L. vegetabilis enlivening, from vegetare to enliven,
   invigorate, quicken, vegetus enlivened, vigorous, active,
   vegere to quicken, arouse, to be lively, akin to vigere to be
   lively, to thrive, vigil watchful, awake, and probably to E.
   wake, v. See Vigil, Wake, v.]
   [1913 Webster]
   1. Of or pertaining to plants; having the nature of, or
      produced by, plants; as, a vegetable nature; vegetable
      growths, juices, etc.
      [1913 Webster]

            Blooming ambrosial fruit
            Of vegetable gold.                    --Milton.
      [1913 Webster]

   2. Consisting of, or comprising, plants; as, the vegetable
      kingdom.
      [1913 Webster]

   Vegetable alkali (Chem.), an alkaloid.

   Vegetable brimstone. (Bot.) See Vegetable sulphur, below.


   Vegetable butter (Bot.), a name of several kinds of
      concrete vegetable oil; as that produced by the Indian
      butter tree, the African shea tree, and the Pentadesma
      butyracea, a tree of the order Guttiferae, also
      African. Still another kind is pressed from the seeds of
      cocoa (Theobroma).

   Vegetable flannel, a textile material, manufactured in
      Germany from pine-needle wool, a down or fiber obtained
      from the leaves of the Pinus sylvestris.

   Vegetable ivory. See Ivory nut, under Ivory.

   Vegetable jelly. See Pectin.

   Vegetable kingdom. (Nat. Hist.) See the last Phrase, below.


   Vegetable leather.
      (a) (Bot.) A shrubby West Indian spurge (Euphorbia
          punicea), with leathery foliage and crimson bracts.
      (b) See Vegetable leather, under Leather.

   Vegetable marrow (Bot.), an egg-shaped gourd, commonly
      eight to ten inches long. It is noted for the very tender
      quality of its flesh, and is a favorite culinary vegetable
      in England. It has been said to be of Persian origin, but
      is now thought to have been derived from a form of the
      American pumpkin.

   Vegetable oyster (Bot.), the oyster plant. See under
      Oyster.

   Vegetable parchment, papyrine.

   Vegetable sheep (Bot.), a white woolly plant (Raoulia
      eximia) of New Zealand, which grows in the form of large
      fleecy cushions on the mountains.

   Vegetable silk, a cottonlike, fibrous material obtained
      from the coating of the seeds of a Brazilian tree
      (Chorisia speciosa). It is used for various purposes, as
      for stuffing cushions, and the like, but is incapable of
      being spun on account of a want of cohesion among the
      fibers.

   Vegetable sponge. See 1st Loof.

   Vegetable sulphur, the fine and highly inflammable spores
      of the club moss (Lycopodium clavatum); witch meal.

   Vegetable tallow, a substance resembling tallow, obtained
      from various plants; as, Chinese vegetable tallow,
      obtained from the seeds of the tallow tree. Indian
      vegetable tallow is a name sometimes given to piney
      tallow.

   Vegetable wax, a waxy excretion on the leaves or fruits of
      certain plants, as the bayberry.
      [1913 Webster]
      [1913 Webster]

   Vegetable kingdom (Nat. Hist.), that primary division of
      living things which includes all plants. The classes of
      the vegetable kingdom have been grouped differently by
      various botanists. The following is one of the best of the
      many arrangements of the principal subdivisions.
      [1913 Webster] I. Phaenogamia (called also
      Phanerogamia). Plants having distinct flowers and true
      seeds. [ 1. Dicotyledons (called also Exogens). --
      Seeds with two or more cotyledons. Stems with the pith,
      woody fiber, and bark concentrically arranged. Divided
      into two subclasses: Angiosperms, having the woody fiber
      interspersed with dotted or annular ducts, and the seeds
      contained in a true ovary; Gymnosperms, having few or no
      ducts in the woody fiber, and the seeds naked. 2.
      Monocotyledons (called also Endogens). -- Seeds with
      single cotyledon. Stems with slender bundles of woody
      fiber not concentrically arranged, and with no true bark.]
      [1913 Webster] II. Cryptogamia. Plants without true
      flowers, and reproduced by minute spores of various kinds,
      or by simple cell division. [ 1. Acrogens. -- Plants
      usually with distinct stems and leaves, existing in two
      alternate conditions, one of which is nonsexual and
      sporophoric, the other sexual and oophoric. Divided into
      Vascular Acrogens, or Pteridophyta, having the
      sporophoric plant conspicuous and consisting partly of
      vascular tissue, as in Ferns, Lycopods, and Equiseta, and
      Cellular Acrogens, or Bryophyta, having the sexual
      plant most conspicuous, but destitute of vascular tissue,
      as in Mosses and Scale Mosses. 2. Thallogens. -- Plants
      without distinct stem and leaves, consisting of a simple
      or branched mass of cellular tissue, or reduced to a
      single cell. Reproduction effected variously. Divided into
      Algae, which contain chlorophyll or its equivalent, and
      which live upon air and water, and Fungi, which contain
      no chlorophyll, and live on organic matter. (Lichens are
      now believed to be fungi parasitic on included algae.]
      [1913 Webster]

   Note: Many botanists divide the Phaenogamia primarily into
         Gymnosperms and Angiosperms, and the latter into
         Dicotyledons and Monocotyledons. Others consider
         Pteridophyta and Bryophyta to be separate classes.
         Thallogens are variously divided by different writers,
         and the places for diatoms, slime molds, and stoneworts
         are altogether uncertain.
         [1913 Webster] For definitions, see these names in the
         Vocabulary.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vegetable \Veg"e*ta*ble\, n.
   1. (Biol.) A plant. See Plant.
      [1913 Webster]

   2. A plant used or cultivated for food for man or domestic
      animals, as the cabbage, turnip, potato, bean, dandelion,
      etc.; also, the edible part of such a plant, as prepared
      for market or the table.
      [1913 Webster]

   3. A person who has permanently lost consciousness, due to
      damage to the brain, but remains alive; sometimes
      continued life requires support by machinery such as
      breathing tubes. Such a person is said to be in a
      vegetative state.
      [PJC]

   Note: Vegetables and fruits are sometimes loosely
         distinguished by the usual need of cooking the former
         for the use of man, while the latter may be eaten raw;
         but the distinction often fails, as in the case of
         quinces, barberries, and other fruits, and lettuce,
         celery, and other vegetables. Tomatoes if cooked are
         vegetables, if eaten raw are fruits.
         [1913 Webster]

WordNet (r) 3.0 (2006):

vegetable
    n 1: edible seeds or roots or stems or leaves or bulbs or tubers
         or nonsweet fruits of any of numerous herbaceous plant
         [syn: vegetable, veggie, veg]
    2: any of various herbaceous plants cultivated for an edible
       part such as the fruit or the root of the beet or the leaf of
       spinach or the seeds of bean plants or the flower buds of
       broccoli or cauliflower

Moby Thesaurus II by Grady Ward, 1.0:

214 Moby Thesaurus words for "vegetable":
   Boston lettuce, Chinese cabbage, French bean, Irish potato, Kraut,
   Swiss chard, amphibian, angiosperm, annual, apathetic,
   aquatic plant, asparagus, aubergine, bean, bean sprout, beans,
   beet, beet greens, beetroot, bell pepper, benumbed, biennial,
   blase, bored, botanic, broccoli, bulbous, butter bean, cabbage,
   carrot, cauliflower, celery, celery cabbage, celery root, celtuce,
   cereal, chard, chick-pea, chicory, collards, contemplative, corn,
   cosmopolite, cress, cucumber, cutting, dead, debilitated,
   deciduous plant, dicot, dicotyledon, do-nothing, dopey, dormant,
   droopy, drugged, dull, eggplant, enervated, ephemeral, evergreen,
   exanimate, exotic, farinaceous, flowering plant, fruitlike, fruity,
   fungus, gametophyte, garlic, green bean, green onion, green pea,
   green pepper, greens, gumbo, gymnosperm, heavy, hebetudinous,
   herbaceous, herbal, herbose, herbous, herby, hominy, horseradish,
   hydrophyte, idle, immobile, inactive, inanimate, inert, jaded,
   kale, kidney beans, kohlrabi, lackadaisical, laissez-aller,
   laissez-faire, languid, languorous, leaden, leek, legumes,
   leguminose, leguminous, lentil, lethargic, lettuce, lifeless,
   listless, love apple, lumpish, mad apple, maize, meditative,
   monocot, monocotyl, moribund, motionless, mushroom, navy bean,
   neuter, neutral, numb, onion, oyster plant, paralytic, paralyzed,
   parsley, parsnip, passive, pea, pepper, perennial, phlegmatic,
   pieplant, pimento, pinto bean, plant, plantlike, polycot,
   polycotyl, polycotyledon, pooped, popcorn, potato, potherbs,
   procrastinating, produce, pumpkin, quiescent, quietist, quietistic,
   radicated, radiciform, radicular, radish, red cabbage, red pepper,
   rhizoid, rhubarb, rootlike, sated, scallion, seed plant, seedling,
   shallot, sleepy, slow, sluggish, somnolent, sorrel, soy, soya,
   spermatophyte, spinach, sporophyte, spud, squash, stagnant,
   stagnating, standpat, static, stationary, stultified, succory,
   sugar beet, supine, swede, sweet potato, taro, tater, thallophyte,
   tomato, torpid, triennial, truffle, tuberous, turnip,
   vascular plant, vegetables, vegetal, vegetarian, vegetational,
   vegetative, wan, water chestnut, weary, weed, weedy, white potato,
   world-weary, yam