A short term bill of exchange, depending on discount to give it value, as it does not pay interest.
Short-term obligations of a Government issued for periods of one year or less. Treasury bills do not carry a rate of interest and are issued at a discount on the par value. Treasury bills are repaid at par on the due date. In the UK they are normally for 91 days, and are offered at weekly tenders. In the US they are auctioned.
Obligations issued by the Department of the Treasury maturing in 13, 26, or 52 weeks.