Find the word definition

Wiktionary
chlorine monofluoride

n. (context inorganic compound English) A gaseous binary compound, CF, of chlorine and fluorine.

Wikipedia
Chlorine monofluoride

Chlorine monofluoride is a volatile interhalogen compound with the chemical formula ClF. It is a colourless gas at room temperature and is stable even at high temperatures. When cooled to −100 °C, ClF condenses as a pale yellow liquid. Many of its properties are intermediate between its parent halogens, Cl and F.