The Collaborative International Dictionary of English v.0.48:

Melon \Mel"on\ (m[e^]l"[u^]n), n. [F., fr. L. melo, for melopepo
   an apple-shaped melon, Gr. mhlope`pwn; mh^lon apple + pe`pwn
   a species of large melon; cf. L. malum apple. Cf.
   Marmalade.]
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   1. (Bot.) The juicy fruit of certain cucurbitaceous plants,
      as the muskmelon, watermelon, and citron melon; also, the
      plant that produces the fruit.
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   2. (Zool.) A large, ornamental, marine, univalve shell of the
      genus Melo.
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   Melon beetle (Zool.), a small leaf beetle (Diabrotiea
      vittata), which damages the leaves of melon vines.

   Melon cactus, Melon thistle.
      (a) (Bot.) A genus of cactaceous plants (Melocactus)
          having a fleshy and usually globose stem with the
          surface divided into spiny longitudinal ridges, and
          bearing at the top a prickly and woolly crown in which
          the small pink flowers are half concealed. Melocactus
          communis, from the West Indies, is often cultivated,
          and sometimes called Turk's cap.
      (b) The related genus Mamillaria, in which the stem is
          tubercled rather than ribbed, and the flowers
          sometimes large. See Illust. under Cactus.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thistle \This"tle\, n. [OE. thistil, AS. [thorn]istel; akin to
   D. & G. distel, OHG. distila, distil, Icel. [thorn]istill,
   Sw. tistel, Dan. tidsel; of uncertain origin.] (Bot.)
   Any one of several prickly composite plants, especially those
   of the genera Cnicus, Craduus, and Onopordon. The name
   is often also applied to other prickly plants.
   [1913 Webster]

   Blessed thistle, Carduus benedictus, so named because it
      was formerly considered an antidote to the bite of
      venomous creatures.

   Bull thistle, Cnicus lanceolatus, the common large
      thistle of neglected pastures.

   Canada thistle, Cnicus arvensis, a native of Europe, but
      introduced into the United States from Canada.

   Cotton thistle, Onopordon Acanthium.

   Fuller's thistle, the teasel.

   Globe thistle, Melon thistle, etc. See under Globe,
      Melon, etc.

   Pine thistle, Atractylis gummifera, a native of the
      Mediterranean region. A vicid gum resin flows from the
      involucre.

   Scotch thistle, either the cotton thistle, or the musk
      thistle, or the spear thistle; -- all used national
      emblems of Scotland.

   Sow thistle, Sonchus oleraceus.

   Spear thistle. Same as Bull thistle.

   Star thistle, a species of Centaurea. See Centaurea.

   Torch thistle, a candelabra-shaped plant of the genus
      Cereus. See Cereus.

   Yellow thistle, Cincus horridulus.
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   Thistle bird (Zool.), the American goldfinch, or
      yellow-bird (Spinus tristis); -- so called on account of
      its feeding on the seeds of thistles. See Illust. under
      Goldfinch.

   Thistle butterfly (Zool.), a handsomely colored American
      butterfly (Vanessa cardui) whose larva feeds upon
      thistles; -- called also painted lady.

   Thistle cock (Zool.), the corn bunting (Emberiza
      militaria). [Prov. Eng.]

   Thistle crown, a gold coin of England of the reign of James
      I., worth four shillings.

   Thistle finch (Zool.), the goldfinch; -- so called from its
      fondness for thistle seeds. [Prov. Eng.]

   Thistle funnel, a funnel having a bulging body and flaring
      mouth.
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