Source : Webster's Revised Unabridged Dictionary (1913)

Guarantee \Guar"an*tee`\, v. t. [imp. & p. p. {guaranteed}; p,
   pr. & vb. n. {Guaranteeing}.] [From {Guarantee}, n.]
   In law and common usage: to undertake or engage for the
   payment of (a debt) or the performance of (a duty) by another
   person; to undertake to secure (a possession, right, claim,
   etc.) to another against a specified contingency, or at all
   avents; to give a guarantee concerning; to engage, assure, or
   secure as a thing that may be depended on; to warrant; as, to
   guarantee the execution of a treaty.

         The United States shall guarantee to every State in
         this Union a republican form of government.
                                                  --Constitution
                                                  of the U. S.