The Collaborative International Dictionary of English v.0.48:

Epitasis \E*pit"a*sis\, n. [NL., fr. Gr. ? a stretching, fr. ?
   to stretch upon or over; 'epi` upon + ? to stretch.]
   1. That part which embraces the main action of a play, poem,
      and the like, and leads on to the catastrophe; -- opposed
      to protasis.
      [1913 Webster]

   2. (Med.) The period of violence in a fever or disease;
      paroxysm. --Dunglison.
      [1913 Webster]