The Collaborative International Dictionary of English v.0.48:

Carbohydrate \Car`bo*hy"drate\, n. [Carbon + hydrate.] (Physiol.
   Chem.)
   One of a group of compounds including the sugars, starches,
   and gums, which contain six (or some multiple of six) carbon
   atoms, united with a variable number of hydrogen and oxygen
   atoms, but with the two latter always in proportion as to
   form water; as dextrose, C6H12O6.
   [1913 Webster]

WordNet (r) 3.0 (2006):

carbohydrate
    n 1: an essential structural component of living cells and
         source of energy for animals; includes simple sugars with
         small molecules as well as macromolecular substances; are
         classified according to the number of monosaccharide groups
         they contain [syn: carbohydrate, saccharide, sugar]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "carbohydrate":
   barley sugar, beet sugar, cellulose, clinical dextran, deoxyribose,
   dextran, dextrose, erythrose, fructose, galactose, glucose,
   glycogen, grape sugar, hydroxy aldehyde, hydroxy ketone, lactose,
   levulose, lyxose, maple sugar, molasses, monosaccharide,
   nipa sugar, pentose sugar, polysaccharide, polysaccharose,
   raffinose, saccharide, starch, sucrose, sugar, tree molasses,
   trisaccharide