The Collaborative International Dictionary of English v.0.48:

Sideboard \Side"board`\, n.
   A piece of dining-room furniture having compartments and
   shelves for keeping or displaying articles of table service.
   [1913 Webster]

         At a stately sideboard, by the wine,
         That fragrant smell diffused.            --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sideboard
    n 1: a removable board fitted on the side of a wagon to increase
         its capacity
    2: a board that forms part of the side of a bed or crib
    3: a piece of furniture that stands at the side of a dining
       room; has shelves and drawers [syn: buffet, counter,
       sideboard]