The Collaborative International Dictionary of English v.0.48:

Assassinate \As*sas"sin*ate\, v. t. [imp. & p. p.
   Assassinated; p. pr. & vb. n. Assassinating.] [LL.
   assassinatus, p. p. of assassinare.]
   1. To kill by surprise or secret assault; to murder by
      treacherous violence.
      [1913 Webster]

            Help, neighbors, my house is broken open by force,
            and I am ravished, and like to be assassinated.
                                                  --Dryden.
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   2. To assail with murderous intent; hence, by extended
      meaning, to maltreat exceedingly. [Archaic]
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            Your rhymes assassinate our fame.     --Dryden.
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            Such usage as your honorable lords
            Afford me, assassinated and betrayed. --Milton.
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   Syn: To kill; murder; slay. See Kill.
        [1913 Webster]

WordNet (r) 3.0 (2006):

assassinated
    adj 1: murdered by surprise attack for political reasons; "the
           20th century has seen too many assassinated leaders"