The Collaborative International Dictionary of English v.0.48:

Lanseh \Lan"seh\ (l[.a]n"s[asl]), n.
   The small, yellow to whitish brown berrylike fruit of an East
   Indian tree (Lansium domesticum). It has a fleshy pulp,
   with an agreeable tart subacid taste. --Balfour.

   Syn: lansah, lansa, lansat, lanset.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

Lansium domesticum
    n 1: East Indian tree bearing an edible yellow berry [syn:
         lanseh tree, langsat, langset, Lansium domesticum]