The Collaborative International Dictionary of English v.0.48:

menthol \men"thol\, n. [Mentha + -ol.] (Chem.)
   A white, crystalline, aromatic substance (C10H20O)
   resembling camphor, extracted from oil of peppermint
   (Mentha); -- called also mint camphor or peppermint
   camphor. It has the peculiar effect on skin and membranes of
   making them feel cool, and is used in liqueurs, confections,
   cigarettes, cough drops and perfumes, among other things.
   [1913 Webster +PJC]