\Mel"on\, n. [F., fr. L. melo, for melopepo an
apple-shaped melon, Gr. ?; ? apple + ? a species of large
melon; cf. L. malum apple. Cf. {Marmalade}.]
1. (Bot.) The juicy fruit of certain cucurbitaceous plants,
   as the muskmelon, watermelon, and citron melon; also, the
   plant that produces the fruit.
2. (Zo["o]l.) A large, ornamental, marine, univalve shell of
   the genus {Melo}.
{Melon beetle} (Zo["o]l.), 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. {M.
       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}.