The Collaborative International Dictionary of English v.0.48:

Ransom \Ran"som\, v. t. [imp. & p. p. Ransomed (-s[u^]md); p.
   pr. & vb. n. Ransoming.] [Cf. F. ran[,c]onner. See
   Ransom, n.]
   1. To redeem from captivity, servitude, punishment, or
      forfeit, by paying a price; to buy out of servitude or
      penalty; to rescue; to deliver; as, to ransom prisoners
      from an enemy.
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   2. To exact a ransom for, or a payment on. [R.]
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            Such lands as he had rule of he ransomed them so
            grievously, and would tax the men two or three times
            in a year.                            --Berners.
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The Collaborative International Dictionary of English v.0.48:

Ransom \Ran"som\ (r[a^]n"s[u^]m), n. [OE. raunson, raunsoun, OF.
   ran[,c]on, raen[,c]on, raan[,c]on, F. ran[,c]on, fr. L.
   redemptio, fr. redimere to redeem. See Redeem, and cf.
   Redemption.]
   1. The release of a captive, or of captured property, by
      payment of a consideration; redemption; as, prisoners
      hopeless of ransom. --Dryden.
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   2. The money or price paid for the redemption of a prisoner,
      or for goods captured by an enemy; payment for freedom
      from restraint, penalty, or forfeit.
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            Thy ransom paid, which man from death redeems.
                                                  --Milton.
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            His captivity in Austria, and the heavy ransom he
            paid for his liberty.                 --Sir J.
                                                  Davies.
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   3. (O. Eng. Law) A sum paid for the pardon of some great
      offense and the discharge of the offender; also, a fine
      paid in lieu of corporal punishment. --Blackstone.
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   Ransom bill (Law), a war contract, valid by the law of
      nations, for the ransom of property captured at sea and
      its safe conduct into port. --Kent.
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WordNet (r) 3.0 (2006):

ransom
    n 1: money demanded for the return of a captured person [syn:
         ransom, ransom money]
    2: payment for the release of someone
    3: the act of freeing from captivity or punishment
    v 1: exchange or buy back for money; under threat [syn:
         ransom, redeem]

The Devil's Dictionary (1881-1906):

RANSOM, n.  The purchase of that which neither belongs to the seller,
nor can belong to the buyer.  The most unprofitable of investments.