noun: (organic chemistry) Any of a class of unsaturated diols of the form R-C(OH)=C(OH)-R for vicinal diols, or -C=C(OH)₂ for geminal diols, often produced by enolization. Alternative names for vicinal diols are ketene hydrate, 1,1-dihydroxyethene, and enolic form of a carboxylic acid.
