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.
      [1913 Webster]

   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]

WordNet (r) 3.0 (2006):

bank note
    n 1: a piece of paper money (especially one issued by a central
         bank); "he peeled off five one-thousand-zloty notes" [syn:
         bill, note, government note, bank bill, banker's
         bill, bank note, banknote, Federal Reserve note,
         greenback]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

BANK NOTE, contracts. A bank note resembles a common promissory note, (q.
v.) issued by a bank or corporation authorized to act as a bank. It is in
fact a promissory note, but such notes are not, for many purposes, to be
considered as mere securities for money; but are treated as money, in the
ordinary course and transactions of business, by the general consent of
mankind and, on payment of them, when a receipt is required, the receipts
are always given as for money, not as for securities or notes. 1 Burr. R.
457; 12 John. R. 200; 1 John. Ch. R. 231; 9 John. R. 120; 19 John. 144; 1
Sch. & Lef. 318, 319; 11 Ves. 662; 1 Roper, Leg. 3; 1 Ham. R. 189, 524; 15
Pick. 177; 5 G. & John. 58; 3 Hawks, 328; 5 J. J. Marsh. 643.
     2. Bank notes are assignable by delivery. Rep. Temp. Hard. 53 9 East,
R. 48; 4 East, R. 510 Dougl. 236. The holder of a bank note is prima facie
entitled to prompt payment of it, and cannot be affected by the fraud of any
former holder in obtaining it, unless evidence be given to bring it home to
his privity. 1 Burr. 452; 4 Rawle, 185 13 East, R. 135 Dane's Ab. Index, h.
t.; Pow. on Mortg. lndex, h. t. U. S. Dig. h. t. Vide Bouv. Inst. Index, h.
t. Note; Promissory note; @Reissuable note.
     3. They cannot be taken in execution. Cunning. on Bills, 537; Hardw.
Cases, 53; 1 Arch. Pr. 268 1 Wils. Rep. 9 Cro. Eliz. 746, pl. 25