Thorium

n.

1.

(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.

Noun

1.

thorium - a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands Synonyms: atomic number 90, Th

atomic number 90, metal, metallic element, monazite, radiothorium, Th, thoriate, thorite, thorium-228