The Collaborative International Dictionary of English v.0.48:

Nitrile \Ni"trile\ (? or ?), n. [See Nitro-.] (Chem.)
   Any one of a series of compounds bearing the cyanide radical
   (-CN); particularly, one of those cyanides of alcohol
   radicals which, by boiling with acids or alkalies, produce a
   carboxyl acid, with the elimination of the nitrogen as
   ammonia.
   [1913 Webster]

   Note: The nitriles are named with reference to the acids
         produced by their decomposition, thus, hydrocyanic acid
         is formic nitrile, methyl cyanide is acetonitrile
         (also acetic nitrile), and ethyl cyanide is
         propionitrile (from propionic acid).
         [1913 Webster +PJC]