oxyl

noun2

1. •
   A compound or radical bound to an oxygen by a single bond

   • If a Type I- or Type II-derived LOOH encounters a ligated Fe2+ or Cu+ on a membrane, it invariably undergoes one-electron reduction to an oxyl radical (LO-) […] — 2007
2. •
   (no longer used) An acid anhydride

   • The formula (CaO, CO2) would represent calcic carbonate as a compound of a base and an oxyl. — 1865