The Collaborative International Dictionary of English v.0.48:

Congou \Con"gou\, Congo \Con"go\, n. [Chin. kung-foo labor.]
   Black tea, of higher grade (finer leaf and less dusty) than
   the present bohea. Also called English breakfast tea. See
   Tea.
   [1913 Webster +PJC]

         Of black teas, the great mass is called Congou, or the
         "well worked", a name which took the place of the Bohea
         of 150 years ago, and is now itself giving way to the
         term "English breakfast tea."            --S. W.
                                                  Williams.
   [1913 Webster]

WordNet (r) 3.0 (2006):

congou
    n 1: black tea grown in China [syn: congou, congo, congou
         tea, English breakfast tea]