Noun tl has 1 sense
  1. thallium, Tl, atomic number 81 - 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
    --1 is a kind of metallic element, metal
    --1 is a substance of zinc blende, blende, sphalerite
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