Thorium \Tho"ri*um\, n. [NL. See {Thorite}.] (Chem.)
A metallic element found in certain rare minerals, as
thorite, pyrochlore, monazite, etc., and isolated as an
infusible gray metallic powder which burns in the air and
forms thoria; -- formerly called also {thorinum}. Symbol Th.
Atomic weight 232.0.
[1913 Webster]