Fucking Railroad Nut; used by railroad employees to describe those who watch and/or photograph trains. Usage has recently fallen off with "foamer" being used in many parts of the country instead
We saw a ton of FRNs stopped by the side of the tracks when the steamer was coming.
by Schnauf March 07, 2006
Federal Reserve Note, a paper printed as to resemble official money, as opposed to gold or silver coin or a United States Note, ostensibly backed by gold and/or silver.
How many FRNs does that cost?
by Peter314 January 17, 2004