tri·lin·gual /-ˈlɪŋgwəl ||ˈlɪŋgjəwəl/
  (a.)三國語的,用三國語言的
  Tri·lin·gual a.  Containing, or consisting of, three languages; expressed in three languages.
     The much-noted Rosetta stone . . . bears upon its surface a trilingual inscription.   --I. Taylor.
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  trilingual
       adj : using or knowing three languages; "trilingual speakers"