The Collaborative International Dictionary of English v.0.48:

Glycol \Gly"col\, n. [Glycerin + -ol. See Glycerin.] (Chem.)
   (a) A thick, colorless liquid, C2H4(OH)2, of a sweetish
       taste, produced artificially from certain ethylene
       compounds. It is a diacid alcohol, intermediate between
       ordinary ethyl alcohol and glycerin.
       [1913 Webster]

WordNet (r) 3.0 (2006):

glycol
    n 1: a sweet but poisonous syrupy liquid used as an antifreeze
         and solvent [syn: ethylene glycol, glycol,
         ethanediol]
    2: any of a class of alcohols having 2 hydroxyl groups in each
       molecule [syn: diol, glycol, dihydric alcohol]