chiasma
chi.as.ma \ki--'az-m*\ \-m*t-*\ \-m*l\ \.ki-*z-'mat-ik\ \ki--'az-mik\ n or chi.as.ma.ta or chiasmas [NL, fr. Gk, crosspiece, fr. chiazein to mark with a chi, fr. chi (] pl x) 1: an anatomical intersection {the optic ~} 2: a fusion and exchange of segments of chromatids between members of a biv alent during meiosis - chi.as.mal aj