What is Caveat?

Legal Definition
Practice. That hebeware. Caveat is the name of a notice given by a party having an interest, to some officer, not to do an act, till the party giving the notice shall have been heard; as, a caveat to the register of wills, or judge of probate, not to permit a will to be proved, or not to grant letters of administration, until the party shall have been heard. A caveat is also frequently made to prevent a patent for inventions being issued. 1 Bouv. Inst. 71, 534; 1 Burn's Ecc. Law, 19, 263; Bac. Abr. Executors and Administrators, E 8; 3 Bl. Com. 246; Proctor's Pract. 68; 3 Bin. Rep. 314; 1 Siderf. 371 Poph. 133; Godolph. Orph. Leg. 258; 2 Brownl. 119; 2 Fonbl. Eq. book 4, pt. 2, c. 1, 3; Ayl. Parer. 145 Nelson's Ab. h. t.; Dane's Ab. c. 223, a. 15, 2, and a. 8, 22. See 2 Chit. Pr. 502, note b, for a form.
-- Bouviers Law Dictionary
Legal Definition
Lat. Let him beware. A formal notice or warning given by a party interested to a court, judge or ministerial officer against the performance of certain acts within his power and jurisdiction. This process may be used in the proper courts to prevent (temporarily or provisionally) the proving of a will or the grant of administration or to arrest the enrollment of a decree in chancery when the party intends to take an appeal, to prevent the grant of letters patent, etc. It is also used, in the American practice, as a kind of equitable process, to stay the granting of a patent for lands. Wilson v. Gaston, 92 Pa. 207; Slocum v. Grandin, 38 N. J. Eq. 485; Ex parte Crafls, 28 S. C. 281, 5 S. E. 718; In re Miller's Estate, 166 Pn. 97, 31 All. 58. In patent law.

A caveat is a formal written notice given to the officers of the patent-office, requiring them to refuse letters patent on a particular invention or device to any other person, until the party filing the caveat (called the "caveator") shall have an opportunity to establish his claim to priority of invention.
-- Black's Law Dictionary
Legal Definition
Let him beware; a notice or warning filed or recorded in a public office so as to prevent anyone from acting to the prejudice of the caveator. See 38 N. J. Eq. 485.
-- Ballentine's Law Dictionary
Legal Definition
"May he beware". When used by itself, refers to a qualification, or warning.