[ kahy-az-muh ]

noun,plural chi·as·mas, chi·as·ma·ta [kahy-az-muh-tuh]. /kaɪˈæz mə tə/.
  1. Anatomy. a crossing or decussation, as that of the optic nerves at the base of the brain.

  2. Cell Biology. a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.

Origin of chiasma

1830–40; <Greek: crosspiece of wood, cross-bandage, equivalent to chichi1 + -asma noun suffix
  • Also chi·asm [kahy-az-uhm]. /ˈkaɪ æz əm/.

Other words from chiasma

  • chi·as·mal, chi·as·mic, chi·as·mat·ic [kahy-az-mat-ik], /ˌkaɪ æzˈmæt ɪk/, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

British Dictionary definitions for chiasma


chiasm (ˈkaɪæzəm)

/ (kaɪˈæzmə) /

nounplural -mas, -mata (-mətə) or -asms
  1. cytology the cross-shaped connection produced by the crossing over of pairing chromosomes during meiosis

  2. anatomy the crossing over of two parts or structures, such as the fibres of the optic nerves in the brain

Origin of chiasma

C19: from Greek khiasma wooden crosspiece, from khiazein to mark with an X, from khi chi 1

Derived forms of chiasma

  • chiasmal or chiasmic, adjective

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012