Meaning of sulfur trioxide

sul'fur triox'ide

Pronunciation: [key]
— Chem. Chem.
  1. an irritant, corrosive, low-melting solid, SO, obtained by the oxidation of sulfur dioxide, used as an intermediate in the manufacture of sulfuric acid. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.