Definition - What does Concealment mean?
Concealment means that an insured has not revealed information that could have affected the policy they bought from the insurer. It can lead to the nullification of the policy, even if the insurer has not asked about that information during the crafting of the policy.
Insuranceopedia explains Concealment
The insured doesn't have to lie directly for the act to be considered concealment. They may simply not have divulged something that will affect an aspect of the insurance like the price of the premium, even if they were not asked about it.
For instance, if the insured was a smoker when they applied for a health insurance but did not reveal it on the application, the insurance company may cancel their policy if this fact is discovered.