The Collaborative International Dictionary of English v.0.48:

Cupbearer \Cup"bear`er\ (-b[^a]r`[~e]r), n.
   1. One whose office it is to fill and hand the cups at an
      entertainment.
      [1913 Webster]

   2. (Antiq.) One of the attendants of a prince or noble,
      permanently charged with the performance of this office
      for his master. "I was the king's cupbearer." --Neh. i.
      11.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cupbearer
    n 1: the attendant (usually an officer of a nobleman's
         household) whose duty is to fill and serve cups of wine

Easton's 1897 Bible Dictionary:

Cup-bearer
   an officer of high rank with Egyptian, Persian, Assyrian, and
   Jewish monarchs. The cup-bearer of the king of Egypt is
   mentioned in connection with Joseph's history (Gen. 40:1-21;
   41:9). Rabshakeh (q.v.) was cup-bearer in the Assyrian court (2
   Kings 18:17). Nehemiah filled this office to the king of Persia
   (Neh. 1:11). We read also of Solomon's cup-bearers (1 Kings
   10:5; 2 Chr. 9:4).