The Collaborative International Dictionary of English v.0.48:

Ptomaine \Pto"ma*ine\, n. [From Gr. ? a dead body.] (Physiol.
   Chem.)
   One of a class of animal bases or alkaloids formed in the
   putrefaction of various kinds of albuminous matter, and
   closely related to the vegetable alkaloids; a cadaveric
   poison. The ptomaines, as a class, have their origin in dead
   matter, by which they are to be distinguished from the
   leucomaines.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ptomaine
    n 1: any of various amines (such as putrescine or cadaverine)
         formed by the action of putrefactive bacteria [syn:
         ptomaine, ptomain]
    2: a term for food poisoning that is no longer in scientific
       use; food poisoning was once thought to be caused by
       ingesting ptomaines [syn: ptomaine, ptomaine poisoning]