Definition of underwrite

• v. t. - To write under something else; to subscribe.
• v. t. - To subscribe one's name to for insurance, especially for marine insurance; to write one's name under, or set one's name to, as a policy of insurance, for the purpose of becoming answerable for loss or damage, on consideration of receiving a certain premium per cent; as, individuals, as well as companies, may underwrite policies of insurance.
• v. i. - To practice the business of insuring; to take a risk of insurance on a vessel or the like.