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 artichoke
    n 1: edible tuber of the Jerusalem artichoke
    2: tall perennial with hairy stems and leaves; widely cultivated
       for its large irregular edible tubers [syn: Jerusalem
       artichoke, girasol, Jerusalem artichoke sunflower,
       Helianthus tuberosus]
    3: sunflower tuber eaten raw or boiled or sliced thin and fried
       as Saratoga chips [syn: Jerusalem artichoke, sunchoke]