The Collaborative International Dictionary of English v.0.48:

Jerusalem \Je*ru"sa*lem\ (j[-e]*r[udd]"s[.a]*l[e^]m), n. [Gr.
   'Ieroysalh`m, fr. Heb. Y[e^]r[=u]sh[=a]laim.]
   The chief city of Palestine, intimately associated with the
   glory of the Jewish nation, and the life and death of Jesus
   Christ.
   [1913 Webster]

   Jerusalem artichoke [Perh. a corrupt. of It. girasole i.e.,
      sunflower, or turnsole. See Gyre, Solar.] (Bot.)
   (a) An American plant, a perennial species of sunflower
       (Helianthus tuberosus), whose tubers are sometimes used
       as food.
   (b) One of the tubers themselves.

   Jerusalem cherry (Bot.), the popular name of either of two
      species of Solanum (Solanum Pseudo-capsicum and
      Solanum capsicastrum), cultivated as ornamental house
      plants. They bear bright red berries of about the size of
      cherries.

   Jerusalem oak (Bot.), an aromatic goosefoot (Chenopodium
      Botrys), common about houses and along roadsides.

   Jerusalem sage (Bot.), a perennial herb of the Mint family
      (Phlomis tuberosa).

   Jerusalem thorn (Bot.), a spiny, leguminous tree
      (Parkinsonia aculeata), widely dispersed in warm
      countries, and used for hedges.

   The New Jerusalem, Heaven; the Celestial City.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Jerusalem thorn
    n 1: thorny Eurasian shrub with dry woody winged fruit [syn:
         Christ's-thorn, Jerusalem thorn, Paliurus spina-
         christi]
    2: spiny tree having dark red edible fruits [syn: jujube,
       jujube bush, Christ's-thorn, Jerusalem thorn, Ziziphus
       jujuba]
    3: large shrub or shrubby tree having sharp spines and pinnate
       leaves with small deciduous leaflets and sweet-scented
       racemose yellow-orange flowers; grown as ornamentals or
       hedging or emergency food for livestock; tropical America but
       naturalized in southern United States [syn: Jerusalem
       thorn, horsebean, Parkinsonia aculeata]
    4: East Indian spiny tree having twice-pinnate leaves and yellow
       flowers followed by flat pods; source of black catechu [syn:
       catechu, Jerusalem thorn, Acacia catechu]