CHIASM

{ Chi″asm (kī″ăz'm), ‖Chi‐as″ma (kī̍‐ăz″mȧ), } n. [[NL. chiasma, fr. Gr. χίασμα two lines placed crosswise, fr. � to mark with a χ.]] (Anat.) A commissure; especially, the optic commissure, or crucial union of the optic nerves. — Chi‐as″mal (�), a..