The Collaborative International Dictionary of English v.0.48:

Apologue \Ap"o*logue\, n. [L. apologous, Gr. ?; ? from + ?
   speech, ? to speak: cf. F. apologue.]
   A story or relation of fictitious events, intended to convey
   some moral truth; a moral fable.
   [1913 Webster]

   Note: An apologue differs from a parable in this;: the
         parable is drawn from events which take place among
         mankind, and therefore requires probability in the
         narrative; the apologue is founded on supposed actions
         of brutes or inanimate things, and therefore is not
         limited by strict rules of probability. [AE]sop's
         fables are good examples of apologues.
         [1913 Webster]

WordNet (r) 3.0 (2006):

apologue
    n 1: a short moral story (often with animal characters) [syn:
         fable, parable, allegory, apologue]