What is Paper Money?

Legal Definition
Any legal document that has monetary value, such as postal orders, checks, cash, as well as promissory notes and any other bills of exchange. Usually, paper money can be easily liquidated.
Legal Definition
By paper money is understood the engagements to pay money which are issued by governments and banks, and which pass as money. Pardes. Dr. Com. n. 9. Bank notes are generally considered as cash, and win answer, all the purposes of currency; but paper money is not a legal tender if objected to. See Bank note, Specie, Tender.
-- Bouviers Law Dictionary
Legal Definition
Bills drawn by a government against its own credit, engaging to pay money, but which do not profess to be immediately convertible into specie, and which are put into compulsory circulation as a substitute for coined money.
-- Black's Law Dictionary
Legal Definition
Same as Greenbacks.
-- Ballentine's Law Dictionary