Real Dictionary

underwrite
verb: If an institution or company underwrites an activity or underwrites the cost of it, they agree to provide any money that is needed to cover losses or buy special equipment, often for an agreed fee.

underwrite in American English
to write under something, esp. under something written; subscribe
intransitive verb: to underwrite something
transitive verb: to write under or at the foot of, esp. under other written matter

underwrite in British English
verb: to undertake to purchase at an agreed price any unsold portion of (a public issue of shares, etc)

underwrite in Finance
verb: If an investment bank underwrites securities, it manages the issuing of securities for a company.

underwrite in Insurance
verb: If an insurer underwrites an insurance policy or a risk, they accept liability if particular losses occur.