noun
thallium
THA-lee-uhm
noun
1
A soft, gray metallic chemical element (symbol Tl, atomic number 81) that tarnishes quickly in air and is highly toxic.
"Thallium was once used in rat poison before its toxicity led to bans."
"The lab handled the thallium sample with extreme care."
How to Use Thallium
Learner’s notesIn plain EnglishA poisonous gray metal used mainly in electronics and, historically, poisons.
Word Forms
thalliums plural
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Etymology
Named from Greek thallos, "green shoot," because the element produces a bright green line in its spectrum.