A "dollar bill" is a common term used to refer to United States currency in the form of a paper note. The term specifically refers to the Federal Reserve Note, which is the most commonly circulated denomination of U.S. currency. These notes are printed and issued by the Bureau of Engraving and Printing, an agency within the U.S. Treasury Department.
The phrase "dollar bill" can also refer to any banknote that is worth one dollar, regardless of its country or origin. However, when speaking specifically about United States currency, the term "one-dollar bill" would be more accurate as it refers only to Federal Reserve Notes in this denomination.
Overall, a "dollar bill" is any paper note that has a face value of one dollar and can be used as legal tender within the United States.