The Collaborative International Dictionary of English v.0.48:

Bicarbonate \Bi*car"bon*ate\, n. [Pref. bi- + carbonate.]
   (Chem.)
   A carbonate in which but half the hydrogen of the acid is
   replaced by a positive element or radical, thus making the
   proportion of the acid to the positive or basic portion twice
   what it is in the normal carbonates; an acid carbonate; --
   sometimes called supercarbonate.
   [1913 Webster] Bicarbureted

WordNet (r) 3.0 (2006):

bicarbonate
    n 1: a salt of carbonic acid (containing the anion HCO3) in
         which one hydrogen atom has been replaced; an acid
         carbonate [syn: bicarbonate, hydrogen carbonate]