The Collaborative International Dictionary of English v.0.48:

gopherwood \gopherwood\ n.
   A small handsome round-headed deciduous tree (Cladrastis
   lutea) having showy white flowers in terminal clusters and
   heavy hardwood yielding yellow dye; also called yellowwood.

   Syn: Kentucky yellowwood, Cladrastis lutea, Cladrastis
        kentukea, yellowwood.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

gopherwood
    n 1: small handsome roundheaded deciduous tree having showy
         white flowers in terminal clusters and heavy hardwood
         yielding yellow dye [syn: Kentucky yellowwood,
         gopherwood, Cladrastis lutea, Cladrastis kentukea]