What is Concealment?

Legal Definition
The act of intentionally not revealing information that should be disclosed and would otherwise affect the terms or creation of a contract. A concealment can occur through either purposeful misrepresentation or withholding of material facts.

Where the information could not have been known by the other party and it is known to be material by the concealing party, the concealment can give grounds for nullifying the contract.
Legal Definition
Contracts. The unlawful suppression of any fact or circumstance, by one of the partis to a contract, from the other, which in justice ought to be made known. 1 Bro. Ch. R. 420; 1 Fonbl. Eq. B. 1, c. 3, 4, note (n); 1 Story, Eq. Jur. 207.

2. Fraud occurs when one person substantially misrepresents or conceals a material fact peculiarly within his own knowledge, in consequence of which a delusion exists; or uses a device naturally calculated to lull the suspicions of a careful man, and induce him to forego inquiry into a matter upon which the other party has information, although such information be not exclusively within his reach. 2 Bl. Com. 451; 3 Id. 166; Sugd. Vend. 1 to 10; 1 Com. Contr. 38; 3 B. & C. 623; 5 D. & R. 490; 2 Wheat. 183; 11 Id. 59; 1 Pet. Sup. C. R. 15, 16. The party is not bound, however, to disclose patent defects. Sugd. Vend. 2.

3. A distinction has been made between the concealment of latent defects in real and personal property. For example, the concealment by an agent that a nuisance existed in connexion with a house the owner had to hire, did not render the lease void. 6 IV. & M. 358. 1 Smith, 400. The rule with regard to personalty is different. 3 Camp. 508; 3 T. R. 759.

4. In insurances, where fairness is so essential to, the contract, a concealment which is only the effect of accident, negligence, inadvertence, or mistake, if material, is equally fatal to the contract as if it were intentional and fraudulent. 1 Bl. R. 594; 3 Burr. 1909. The insured is required to disclose all the circumstances within his own knowledge only, which increase the risk. He is not, however, bound to disclose general circumstances which apply to all policies of a particular description, notwithstanding they may greatly increase the risk. Under this rule, it has been decided that a policy is void, which was obtaineed by the concealment by the assured of the fact that he had heard that a vessel like his was taken. 2 P. Wms. 170. And in a case where the assured had information of "a violent storm" about eleven hours after his vessel had sailed, and had stated only that "there had been blowing weather and severe storms on the coast after the vessel had sailed" but without any reference to the particular storm it was decided that this was a concealment, which vitiated the policy. 2 Caines R. 57. Vide 1 Marsh. Ins: 468; Park, Ins. 276; 14 East, R. 494; 1 John. R. 522; 2 Cowen, 56; 1 Caines, 276; 3 Wash. C. C. Rep. 138; 2 Gallis. 353; 12 John. 128.

5. Fraudulent concealment avoids the contract. See, generally, Verpl. on Contr. passim; Bouv. Inst. Index, h. t.; Marsh. Ins. B. 1, c. 9; 1 Bell's Com. B. 2, pt. 3, c. 15 s. 3, 1; 1 M. & S. 517; 2 Marsh. R. 336.
-- Bouviers Law Dictionary
Legal Definition
The improper suppression or disguising of a fact, circumstance, or qualification which rests within the knowledge of one only of the parties to a contract, but which ought in fairness and good faith to be communicated to the other, whereby the party so concealing draws the other into an engagement which he would not make but for his ignorance of the fact concealed. A neglect to communicate that which a party knows, and ought to communicate, is called a "concealment." Civ. Code Cah ยง 256L

The terms "misrepresentation" and "concealment" have a known and definite meaning in the law of insurance. Misrepresentation is the statement of something as fact which is untrue in fact, and which the assured states, knowing it to be not true, with an intent to deceive the underwriter, or which he states positively as true, without knowing it to be true, and which has a tendency in mislead, such fact in either case being material to the risk.

Concealment is the designed and intentional withholding of any fact material to the risk, which the assured, in honesty and good faith, ought to communicate to the underwriter j mere silence on the part of the assured, especially as to some matter of fact which he does not consider it important for the underwriter to know, is not to be considered as such concealment. If the fact so untruly stated or purposely suppressed is not material, that is, if the knowledge or ignorance of it would not naturally influence the judgment of the underwriter in making the contract, o in estimating the degree and character of the risk, or in fixing the rate of the premium, it is not a "misrepresentation" or "concealment," within the clause of the conditions annexed to policies. Daniels v. Insurance Co., 12 Cush. (Mass.) 416, 59 Am. Dec. 192.
-- Black's Law Dictionary
Legal Definition
A suppression or neglect to disclose that which one knows and ought to communicate. See 3 Conn. 413.
-- Ballentine's Law Dictionary