The Collaborative International Dictionary of English v.0.48:

opepe \opepe\ n.
   A large African forest tree (Nauclea diderrichii) yielding
   a strong hard yellow to golden brown lumber; sometimes placed
   in genus Sarcocephalus, and then called Sarcocephalus
   diderrichii.

   Syn: Nauclea diderrichii, Sarcocephalus diderrichii.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Sarcocephalus diderrichii
    n 1: large African forest tree yielding a strong hard yellow to
         golden brown lumber; sometimes placed in genus
         Sarcocephalus [syn: opepe, Nauclea diderrichii,
         Sarcocephalus diderrichii]