1) Compound containing O3 2) Oxide 
A trioxide is a compound with three oxygen atoms. For metals with the M2O3 formula there are several common structures. Al2O3, Cr2O3, Fe2O3, and V2O3 adopt the corundum structure. Many rare earth oxides adopt the `A-type rare earth structure` which is hexagonal. Several others plus indium oxide adopt the `C-type rare earth structure`, also cal...
• (n.) An oxide containing three atoms of oxygen; as, sulphur trioxide, SO3; -- formerly called tritoxide.
Type: Term Pronunciation: trī-oks′īd Definitions: 1. A molecule containing three atoms of oxygen. Synonyms: teroxide
In chemistry, a trioxide is a compound with three atoms of oxygen with an element or radical.
[n] - an oxide containing three atoms of oxygen in the molecule
trioxide An oxide containing three oxygen atoms per molecule.
In chemistry, a trioxide is a compound with three atoms of oxygen with an element or radical. 
noun an oxide containing three atoms of oxygen in the molecule