[k??'azm?, k?-]
¦ noun (plural chiasmata -t?)
1. (also optic chiasma) Anatomy the X-shaped structure formed at the point below the brain where the two optic nerves cross over each other.
2. Biology a point at which paired chromosomes remain in contact during the first metaphase of meiosis.
Origin
C19: mod. L., from Gk chiasma 'crosspiece, cross-shaped mark', from khiazein 'mark with the letter chi'.