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1.
FSN
acronym,
F.S.N stands for F*ck School N*gga
John: Too many homework dude!
Jim: Yeah FSN man!
by Alejandro DaPizzi September 03, 2012
 
2.
Fsn
Former slave name. Used by African Americans particularly of the 1960s Black Power generation to describe the rejected names they were born with.
On May 2 1973, Black Panther activist Assata Shakur (fsn) JoAnne Chesimard, was pulled over by the New Jersey State Police, shot twice and then charged with murder of a police officer
by Mattolejack December 30, 2011
 
3.
fsn
acrynom for Fat Slag Nan.

someone's nan who is fat, and was a slag in her youth.
Dave: Did you hear about Jonny's nan the other night?
Bill: Yeah, shes such a fsn!
by mateeeee. July 06, 2009