A document issued by a bank that guarantees the payment of a customer's draft; substitutes the bank's credit for the customer's credit WordNet 3.0 & Open English WordNet

A letter of credit, also known as a documentary credit or bankers commercial credit, or letter of undertaking, is a payment mechanism used in international trade to provide an economic guarantee from a creditworthy bank to an exporter of goods. Wikipedia

A document issued to provide a payment undertaking Wikipedia Disambiguation

A document, used primarily in trade finance and issued generally by a financial institution, in which the institution promises to pay debts up to a certain limit to be acquired by the beneficiary against delivery of documents specified in the letter. Wiktionary

Trade finance document. Wiktionary (translation)