(US) Initialism of Federal Bureau of Investigation. / (Britain) Federation of British Industry (1916–1965), forerunner of CBI (Confederation of British Industry).

Fixed-bit index. / (US, humorous) Female body inspector.

plural of FBIer

(informal, rare) An FBI agent.

(biochemistry, bacteriology) A gene found in Mycobacterium bovis that codes an enzyme involved in the production of coenzyme F₄₂₀-5.