chiasma

UK: /kaɪˈæzmə/ US: (kī az′mə)

Inflections of 'chiasma' (n):

chiasmas

npl

chiasmata

npl

WordReference Random House Unabridged Dictionary of American English © 2025

chi•as•ma  (kī az′mə), n., pl. -mas, -ma•ta 

(-mə tə). 
1. Anatomy a crossing or decussation, as that of the optic nerves at the base of the brain.
2. [Cell Biol.] a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.

Also, chi•asm  (kī′az əm). 

• Greek: crosspiece of wood, cross-bandage, equivalent. to chi chi¹ + -asma noun, nominal suffix
• 1830–40;

chi•as′mal, chi•as′mic, chi•as•mat•ic  (kī′az mat′ik), adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

chiasma / kaɪˈæzmə/, chiasm / ˈkaɪæzəm/ noun ( -mas, -mata / -mətə/, -asms)

1. the cross-shaped connection produced by the crossing over of pairing chromosomes during meiosis
2. the crossing over of two parts or structures, such as the fibres of the optic nerves in the brain

Etymology: 19th Century: from Greek khiasma wooden crosspiece, from khiazein to mark with an X, from khi chi¹