The Collaborative International Dictionary of English v.0.48:

Surety \Sure"ty\, n.; pl. Sureties. [OE. seurte, OF.
   se["u]rt['e], F. s[^u]ret['e]. See Sure, Security.]
   1. The state of being sure; certainty; security.
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            Know of a surety, that thy seed shall be a stranger
            in a land that is not theirs.         --Gen. xv. 13.
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            For the more surety they looked round about. --Sir
                                                  P. Sidney.
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   2. That which makes sure; that which confirms; ground of
      confidence or security.
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            [We] our happy state
            Hold, as you yours, while our obedience holds;
            On other surety none.                 --Milton.
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   3. Security against loss or damage; security for payment, or
      for the performance of some act.
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            There remains unpaid
            A hundred thousand more; in surety of the which
            One part of Aquitaine is bound to us. --Shak.
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   4. (Law) One who is bound with and for another who is
      primarily liable, and who is called the principal; one who
      engages to answer for another's appearance in court, or
      for his payment of a debt, or for performance of some act;
      a bondsman; a bail.
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            He that is surety for a stranger shall smart for it.
                                                  --Prov. xi.
                                                  15.
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   5. Hence, a substitute; a hostage. --Cowper.
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   6. Evidence; confirmation; warrant. [Obs.]
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            She called the saints to surety,
            That she would never put it from her finger,
            Unless she gave it to yourself.       --Shak.
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