Contestability
Contestability is the legal right of the insurance company to question (i.e. ‘contest’) your insurance coverage.
If the insurance company finds that the insured person(s) gave incomplete or incorrect information when applying for the insurance, they will look at what impact the missing information would have had on their decision to offer insurance.
If the insurance company's decision would have been different, they may cancel your coverage and/or deny claims.
Most policies have a two-year contestability period. After the 2-year period, the insurance company cannot contest your coverage except in the case of fraud (a deliberate misstatement of fact).
E.g. a smoker who states in their application that they’re a non-smoker, to get a reduced premium.