The Collaborative International Dictionary of English v.0.48:

Sycamore \Syc"a*more\, n. [L. sycomorus, Gr. ? the fig mulberry;
   ? a fig + ? the black mulberry; or perhaps of Semitic origin:
   cf. F. sycomore. Cf. Mulberry.] (Bot.)
   (a) A large tree (Ficus Sycomorus) allied to the common
       fig. It is found in Egypt and Syria, and is the sycamore,
       or sycamine, of Scripture.
   (b) The American plane tree, or buttonwood.
   (c) A large European species of maple (Acer
       Pseudo-Platanus). [Written sometimes sycomore.]
       [1913 Webster]

WordNet (r) 3.0 (2006):

Ficus sycomorus
    n 1: thick-branched wide-spreading tree of Africa and adjacent
         southwestern Asia often buttressed with branches rising
         from near the ground; produces cluster of edible but
         inferior figs on short leafless twigs; the biblical
         sycamore [syn: sycamore, sycamore fig, mulberry fig,
         Ficus sycomorus]