chiasma
noun
chi·as·ma kī-ˈaz-mə 
kē-
plural chiasmata kī-ˈaz-mə-tə
kē-
1
: an anatomical intersection or decussation compare optic chiasma
2
: a cross-shaped configuration of paired chromatids visible in the diplotene stage of meiotic prophase and considered the cytological equivalent of genetic crossing-over
chiasmatic
ˌkī-əz-ˈma-tik
adjective ˌkē-
Word History
Etymology
New Latin, X-shaped configuration, from Greek, crosspiece, from chiazein to mark with a chi, from chi (x)
First Known Use
1839, in the meaning defined at sense 1
Phrases Containing chiasma
Medical Definition
chiasma
noun
chi·as·ma kī-ˈaz-mə, kē-
plural chiasmata -mət-ə
1
: an anatomical intersection or decussation see optic chiasma
2
: a cross-shaped configuration of paired chromatids visible in the diplotene of meiotic prophase and considered the cytological equivalent of genetic crossing-over