epistasis

‖n. [ NL., fr. Gr. &unr_; a stretching, fr. &unr_; to stretch upon or over; 'epi` upon + &unr_; 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 ]