Found 2 items, similar to thallium.
English → English (WordNet) Definition: thallium thallium n : a soft gray 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 [syn: Tl, atomic number 81]
English → English (gcide) Definition: Thallium Thallium \Thal"li*um\, n. [NL., fr. Gr. ? young or green shoot or branch, twig. So called from a characteristic bright green line in its spectrum.] (Chem.) A rare metallic element of the aluminium group found in some minerals, as certain pyrites, and also in the lead-chamber deposit in the manufacture of sulphuric acid. It is isolated as a heavy, soft, bluish white metal, easily oxidized in moist air, but preserved by keeping under water. Symbol Tl. Atomic weight 203.7. [1913 Webster]