From The Collaborative International Dictionary of English v.0.48:
banknote \bank"note`\, bank note \bank"
note`\(b[a^][ng]k"n[=o]t`).
1. A promissory note issued by a bank or banking company,
payable to the bearer on demand. See also sense 4.
[1913 Webster]
Note: In the United States popularly called a bank bill.
[1913 Webster]
2. Formerly, a promissory note made by a banker, or banking
company, payable to a specified person at a fixed date; a
bank bill. See Bank bill, 2. [Obs.]
[1913 Webster]
3. A promissory note payable at a bank.
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4. A promissory note issued by an authorized bank, payable to
the bearer on demand and intended to circulate as
government-authorized money; in the United States such
notes may only be issued by a Federal Reserve Bank; as, he
peeled off five one-thousand-zloty banknotes.
Syn: bill, note, government note, bank bill, banker's bill,
bank note, Federal Reserve note, greenback.
[1913 Webster +PJC]