un‧der‧write past tense underwrote past participle underwritten [transitive]
to support an activity, business plan etc with money, and to take financial responsibility if it fails:
The government has agreed to underwrite the project with a grant of £5 million.
if an insurance company underwrites an insurance contract, it agrees to pay for any damage or loss that happens
to arrange to sell shares to investors, and to agree to buy any which are not bought by them
—underwriter noun [countable]