Insurability can mean either whether a particular type of loss (risk) can be insured in theory, or whether a particular client is insurable for by a particular company because of particular circumstance and the quality assigned by an insurance provider pertaining to the risk that a given client would have.
An individual with very low insurability may be said to be uninsurable, and an insurance company will refuse to issue a policy to such an applicant. For example, an individual with a terminal illness and a life expectency of 6 months would be uninsurable for term life insurance. This is because the probability is so high for the individual to die within the term of the insurance, that he/she would present much too high a liability for the insurance company. A similar, and stereotypical, example would be earthquake insurance in California.
Insurability is sometimes an issue in case law of torts and contracts. It also comes up in issues involving tontines and other insurance fraud schemes. In real property law and real estate, insurability of title means the realty is marketable.