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Webster 1913 Edition

Noun.

One who cautions or advises.

(Scots Law)

A surety or sponsor.

Noun.

In Scots law, the person who is bound for another, to the performance of an obligation.

cautioner ‎(plural cautioners)

A person who cautions.
(Scotland) A surety.
- 1693, James Dalrymple Stair, The institutions of the law of Scotland (page 755)
  Fourteen Days are only allowed for Sists of Execution, from the Date the Bill was signed, for the Clerks inquiring in the Condition of the Cautioner […]