The Collaborative International Dictionary of English v.0.48:

Aldol \Al"dol\, n. [Aldehyde + -ol as in alcohol.] (Chem.)
   A colorless liquid, C4H8O2, obtained by condensation of two
   molecules of acetaldehyde: CH3CHO + CH3CHO = H3CH(OH)CH2CO;
   also, any of various derivatives of this. The same reaction
   has been applied, under the name of

   aldol condensation, to the production of many compounds.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

aldol
    n 1: an oily colorless liquid obtained by the condensation of
         two molecules of acetaldehyde; contains an alcohol group
         (-OH) and an aldehyde group (-CHO) [syn: aldol,
         aldehyde-alcohol]