Dictionary.net

To make sure or secure; as, to insure safety to any one.

Specifically, to secure against a loss by a contingent event, on certain stipulated conditions, or at a given rate or premium; to give or to take an insurance on or for; as, a merchant insures his ship or its cargo, or both, against the dangers of the sea; goods and buildings are insured against fire or water; persons are insured against sickness, accident, or death; and sometimes hazardous debts are insured.

To make sure or secure; as, to insure safety to any one.

Specifically, to secure against a loss by a contingent event, on certain stipulated conditions, or at a given rate or premium; to give or to take an insurance on or for; as, a merchant insures his ship or its cargo, or both, against the dangers of the sea; goods and buildings are insured against fire or water; persons are insured against sickness, accident, or death; and sometimes hazardous debts are insured.

To make a formal agreement on certain conditions to secure against loss or damage by fire, death, accident, etc.; make sure or secure.

To undertake or contract to give security against loss by fire, etc.; to underwrite.

To make sure or secure: to contract for a premium to make good a loss, as from fire, etc., or to pay a certain sum on a certain event, as death.

To practice making insurance.

To make sure; to secure against loss.

To make sure; guarantee.

To effect insurance.

To make sure or secure; to contract for a premium to secure against loss.

To practise making insurance.

To engage to make good to another the loss, as by fire or at sea, of any specified property, at a certain rate per cent; ensure is the spelling when the sense is "to make sure or certain"; to engage to pay a certain sum on the arrival of some event, as on the death of a person or the loss of property by fire; the terms assure and assurance are now usually restricted to life.