Funds that invest in Treasury bills, or T-bills, which are short-term I.O.U.s to the U.S. Treasury. These funds typically pay the lowest yields but are considered the least risky money funds.
U.S. TREASURY-ONLY MONEY FUNDS
Meaning of U.S. TREASURY-ONLY MONEY FUNDS in English
Mutual Fund English Glossary. Английский глоссарий взаимных и инвестиционных фондов. 2012