The Collaborative International Dictionary of English v.0.48:

Caveat \Ca"ve*at\, n. [L. caved let him beware, pres. subj. of
   cavere to be on one's guard to, beware.]
   [1913 Webster]
   1. (Law) A notice given by an interested party to some
      officer not to do a certain act until the party is heard
      in opposition; as, a caveat entered in a probate court to
      stop the proving of a will or the taking out of letters of
      administration, etc. --Bouvier.
      [1913 Webster]

   2. (U. S. Patent Laws) A description of some invention,
      designed to be patented, lodged in the patent office
      before the patent right is applied for, and operating as a
      bar to the issue of letters patent to any other person,
      respecting the same invention.
      [1913 Webster]

   Note: A caveat is operative for one year only, but may be
         renewed.
         [1913 Webster]

   3. Intimation of caution; warning; protest.
      [1913 Webster]

            We think it right to enter our caveat against a
            conclusion.                           --Jeffrey.
      [1913 Webster]

   Caveat emptor [L.] (Law), let the purchaser beware, i. e.,
      let him examine the article he is buying, and act on his
      own judgment.
      [1913 Webster]

WordNet (r) 3.0 (2006):

caveat emptor
    n 1: a commercial principle that without a warranty the buyer
         takes upon himself the risk of quality

Bouvier's Law Dictionary, Revised 6th Ed (1856):

CAVEAT EMPTOR. Let the purchaser take heed; that is, let him see to it, that
the title he is buying is good. This is a rule of the common law, applicable
to the sale and purchase of lands and other real estate. If the purchaser
pay the consideration money, he cannot, as a general rule, recover it back
after the deed has been executed; except in cases of fraud, or by force of
some covenant in the deed which has been broken. The purchaser,if he fears a
defect of title, has it in his power to protect himself by proper covenants,
and if he fails to do so, the law provides for him no remedy. Cro. Jac. 197;
1 Salk. 211 Doug. 630, 654; 1 Serg. & R. 52, 53, 445. This rule is
discussed with ability in Rawle on Covenants for Title, p. 458, et seq. c.
13, and the leading authorities collected. See also 2 Kent, Com. Lect. 39,
p. 478; 2 Bl. Com. 451; 1 Stor, Eq. Sec. 212 6 Ves. 678; 10 Ves. 505; 3
Cranch, 270; 2 Day, R. 128; Sugd. Vend. 221 1 Bouv. Inst. n. 954-5.
     2. This rule has been severely assailed, as being the instrument of
falsehood and fraud; but it is too well established to be disregarded.
Coop., Just. 611, n. See 8 Watts, 308, 309.