The Collaborative International Dictionary of English v.0.48:

Murder \Mur"der\, v. t. [imp. & p. p. Murdered
   (m[^u]r"d[~e]rd); p. pr. & vb. n. Murdering.] [OE.
   mortheren, murtheren, AS. myr[eth]rian; akin to OHG.
   murdiren, Goth. ma['u]r[thorn]rjan. See Murder, n.]
   1. To kill with premediated malice; to kill (a human being)
      willfully, deliberately, and unlawfully. See Murder, n.
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   2. To destroy; to put an end to.
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            [Canst thou] murder thy breath in middle of a word?
                                                  --Shak.
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   3. To mutilate, spoil, or deform, as if with malice or
      cruelty; to mangle; as, to murder the king's English.
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   Syn: To kill; assassinate; slay. See Kill.
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The Collaborative International Dictionary of English v.0.48:

Murder \Mur"der\ (m[^u]r"d[~e]r), n. [OE. morder, morther, AS.
   mor[eth]or, fr. mor[eth] murder; akin to D. moord, OS.
   mor[eth], G., Dan., & Sw. mord, Icel. mor[eth], Goth.
   ma['u]r[thorn]r, OSlav. mr[=e]ti to die, Lith. mirti, W. marw
   dead, L. mors, mortis, death, mori, moriri, to die, Gr.
   broto`s (for mroto`s) mortal, 'a`mbrotos immortal, Skr. m[.r]
   to die, m[.r]ta death. [root]105. Cf. Amaranth, Ambrosia,
   Mortal.]
   The offense of killing a human being with malice prepense or
   aforethought, express or implied; intentional and unlawful
   homicide. "Mordre will out." --Chaucer.
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         The killing of their children had, in the account of
         God, the guilt of murder, as the offering them to idols
         had the guilt of idolatry.               --Locke.
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         Slaughter grows murder when it goes too far. --Dryden.
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   Note: Murder in the second degree, in most jurisdictions, is
         a malicious homicide committed without a specific
         intention to take life. --Wharton.
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WordNet (r) 3.0 (2006):

murder
    n 1: unlawful premeditated killing of a human being by a human
         being [syn: murder, slaying, execution]
    v 1: kill intentionally and with premeditation; "The mafia boss
         ordered his enemies murdered" [syn: murder, slay,
         hit, dispatch, bump off, off, polish off,
         remove]
    2: alter so as to make unrecognizable; "The tourists murdered
       the French language" [syn: mangle, mutilate, murder]