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.

Source: Webster's Revised Unabridged Dictionary (1913)