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

 

thallium

 noun
noun
BrE BrE//ˈθæliəm//
 
; NAmE NAmE//ˈθæliəm//
 
[uncountable](symbol Tl)
 
jump to other results
a chemical element. Thallium is a soft silver-white metal whose compounds are very poisonous. Word Origin mid 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