To make sure, certain, or secure; give assurance of; assure: as, to insure safety to any one.Specifically To guarantee or secure indemnity for future loss or damage (as to a building from fire, or to a person from accident or death) on certain stipulated conditions; make a subject of insurance; assure: as, to insure a ship or its cargo, or both, against the dangers of the sea; to insure a house against fire.To pledge; betroth.Synonyms Insure, Assure. Assure may express the making certain in mind: as, I was assured of safety by his friendly manner; insure has not this sense. Insure is a possible word to express the making certain in fact, and is more common than ensure: as, his lack of money insured his early return; assure has not this sense. Insure and assure are both used of the act of pledging a payment of money upon loss or death, but assure is rarely used in that sense in the United States.To undertake to secure or assure against loss or damage on receipt of a certain payment or premium; make insurance: as, the company insures at a low premium.