- a colorless, oily liquid, C5H4O2, having an aromatic odor, obtained from bran, sugar, wood, corncobs, or the like, by distillation: used chiefly in the manufacture of plastics and as a solvent in the refining of lubricating oils.
- A colorless, sweet-smelling, liquid made from corncobs and used as a solvent in petroleum refining and as a fungicide and weed killer. It turns reddish brown when exposed to air and light. Furfural is an aldehyde of furan. Chemical formula: C5H4O2.