The Collaborative International Dictionary of English v.0.48:

Acrolein \A*cro"le*in\, n. [L. acer sharp + ol[=e]re to smell.]
   (Chem.)
   A limpid, colorless, highly volatile liquid, obtained by the
   dehydration of glycerin, or the destructive distillation of
   neutral fats containing glycerin. Its vapors are intensely
   irritating. --Watts.
   [1913 Webster]

WordNet (r) 3.0 (2006):

acrolein
    n 1: a pungent colorless unsaturated liquid aldehyde made from
         propene [syn: propenal, acrolein]