Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun thallium

1 sense of thallium

Sense 1
thallium, Tl, atomic number 81 -- (a soft grey malleable metallic element that resembles tin but discolors on exposure to air; it is highly toxic and is used in rodent and insect poisons; occurs in zinc blende and some iron ores)
       => metallic element, metal -- (any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.)