Definition of octatomic in English:

octatomic

Pronunciation /ˌɒktəˈtɒmɪk/

adjective

Chemistry
  • Consisting of eight atoms; containing eight atoms per molecule.

Origin

Late 19th century. From octo- + atomic. Compare earlier monatomic, diatomic, triatomic, tetratomic, pentatomic, hexatomic, heptatomic.