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An initialism of "first name unknown," used especially in law enforcement. Sometimes spelled "Fnu," especially when used in combination with "Lnu" ("last name unknown"). The report lists the suspect's name as Smith, FNU. The court docket names "Fnu Lnu" as the primary suspect in the murder case.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.