A written legal document defining the parties' rights and liabilities to one another. negotiable instrument. Under the Uniform Commercial Code, a writing that reflects an unconditional promise to pay, such as a check or note, but does not also include security for the payment. n. insufficient evidence Evidence so inadequate to prove an assertion that it will not even support a presumption. insurable interest See interest. n. insurance An agreement by an insurer to provide compensation or anot...