DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   Tl
       n 1: 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 [syn: thallium, Tl, atomic number
    81]