The Collaborative International Dictionary of English v.0.48:
Synizesis \Syn`i*ze"sis\, n. [L., fr. Gr. ?, fr. ? to sit together; sy`n with + ? to sit.] 1. (Med.) An obliteration of the pupil of the eye. [1913 Webster] 2. (Gram.) A contraction of two syllables into one; synecphonesis. [1913 Webster]WordNet (r) 3.0 (2006):
synizesis n 1: the contraction of chromatin towards one side of the nucleus during the prophase of meiosis [syn: synizesis, synezesis]