The Collaborative International Dictionary of English v.0.48:

Caution \Cau"tion\, n. [F. caution a security, L. cautio, fr.
   cavere (For scavere) to be on one's guard, to take care
   (orig.) to be on the watch, see; akin to E. show.]
   1. A careful attention to the probable effects of an act, in
      order that failure or harm may be avoided; prudence in
      regard to danger; provident care; wariness.
      [1913 Webster]

   2. Security; guaranty; bail. [R.]
      [1913 Webster]

            The Parliament would yet give his majesty sufficient
            caution that the war should be prosecuted.
                                                  --Clarendon.
      [1913 Webster]

   3. Precept or warning against evil of any kind; exhortation
      to wariness; advice; injunction.
      [1913 Webster]

            In way of caution I must tell you.    --Shak.
      [1913 Webster]

   4. (Civil & Scots Law) A pledge, bond, or other security for
      the performance of an obligation either in or out of
      judicial proceedings; the promise or contract of one not
      for himself but another; security.
      [Webster 1913 Suppl.]

   Caution money, money deposited by way of security or
      guaranty, as by a student at an English university.

   Syn: Care; forethought; forecast; heed; prudence;
        watchfulness; vigilance; circumspection; anxiety;
        providence; counsel; advice; warning; admonition.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Caution \Cau"tion\ v. t. [imp. & p. p. Cautioned; p. pr. & vb.
   n. Cautioning.]
   To give notice of danger to; to warn; to exhort [one] to take
   heed.
   [1913 Webster]

         You cautioned me against their charms.   --Swift.
   [1913 Webster]

WordNet (r) 3.0 (2006):

caution
    n 1: the trait of being cautious; being attentive to possible
         danger; "a man of caution" [syn: caution, cautiousness,
         carefulness] [ant: incaution, incautiousness]
    2: a warning against certain acts; "a caveat against unfair
       practices" [syn: caution, caveat]
    3: judiciousness in avoiding harm or danger; "he exercised
       caution in opening the door"; "he handled the vase with care"
       [syn: caution, precaution, care, forethought]
    4: the trait of being circumspect and prudent [syn:
       circumspection, caution]
    v 1: warn strongly; put on guard [syn: caution, admonish,
         monish]