underwriter
noun
[ ˈʌndərʌɪtə ]
• a person or company that underwrites an insurance risk.
• "none of the five main British insurance underwriters would be willing to offer cover"
• a bank or other financial institution that pledges to buy all the unsold shares in an issue of new shares.
• "the issues are guaranteed success as the underwriters will buy whatever is not snapped up by the market"
