Source : Webster's Revised Unabridged Dictionary (1913)

Epochal \Ep"o*chal\, a.
   Belonging to an epoch; of the nature of an epoch. ``Epochal
   points.'' --Shedd.

Source : WordNet®

epochal
     adj : highly significant or important especially bringing about or
           marking the beginning of a new development or era;
           "epochal decisions made by Roosevelt and Churchill";
           "an epoch-making discovery" [syn: {epoch-making}]