Definition of chlorine tetroxide in US English:

chlorine tetroxide

noun

Chemistry
  • Any of several unstable or hypothetical oxides believed to contain chlorine in the +7 oxidation state, as ClO₄, thought to exist only as a reaction intermediate, and ClOClO₃ (dichlorine tetroxide or chlorine perchlorate), a pale greenish liquid which decomposes at room temperature.

Origin

Mid 19th century.