joking alteration of the name of the FederalBureau of Investigation, a branch of the US Department of Justice, responsible for investigating violations of federal law. —basicdefinition of FBI from Deterioration of Liberty Glossary, Final approval 17.9.89 5th ACC Glossary Part 1 (Final approval 2.12.89) also 5th ACC Vol 2 Glossary (Final Approval 7/12/89)