thallium

noun

thal·​li·​um ˈtha-lē-əm 

: a soft poisonous metallic element that resembles lead in physical properties, occurs sparsely in a number of common ores, and is used chiefly in the form of compounds especially in photosensitive devices and formerly as a pesticide see Chemical Elements Table

Examples of thallium in a Sentence

Recent Examples on the Web

The girls died in April after allegedly ingesting raspberries contaminated with thallium, a highly dangerous and odorless metal, the publication reported. —Becca Longmire, PEOPLE, 18 Dec. 2025

According to the complaint, Hanmer watched a video on how to create thallium sulfate on April 5 and May 15. —Trent Abrego, Twin Cities, 6 Sep. 2025

No one needs to convince a soul that Colman is one of the single best reasons to keep watching movies and TV today, and that her talent for lacing a twinkle with high degrees of thallium is damn near peerless. —David Fear, Rolling Stone, 27 Aug. 2025

In April, her gym water bottle was allegedly contaminated with cyanide and thallium after her car was broken into, prosecutors said, according to WKOW. —Samira Asma-Sadeque, People.com, 24 June 2025

Word History

Etymology

New Latin, from Greek thallos green shoot; from the bright green line in its spectrum

First Known Use

1861, in the meaning defined above

Rhymes for thallium

• allium
• gallium
• pallium

Kids Definition

thallium

noun

thal·​li·​um ˈthal-ē-əm 

: a soft poisonous metallic element that has characteristics similar to lead see element

Medical Definition

thallium

noun

thal·​li·​um ˈthal-ē-əm 

: a sparsely but widely distributed poisonous metallic element that resembles lead in physical properties and is used chiefly in the form of compounds in photoelectric cells or as a pesticide

—symbol Tl see Chemical Elements Table