Definition of thallium noun from the Oxford Advanced Learner's Dictionary



BrE BrE//ˈθæliəm//
; NAmE NAmE//ˈθæliəm//
[uncountable] (symbol Tl)
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a chemical element. Thallium is a soft silver-white metal whose compounds are very poisonous. Word Originmid 19th cent.: modern Latin, from Greek thallos ‘green shoot’, because of the green line in its spectrum.
See the Oxford Advanced American Dictionary entry: thallium