the Federal Bureau of Investigation
noun🔊/ðə ˌfedərəl ˌbjʊərəʊ əv ɪnˌvestɪˈɡeɪʃn/
🔊/ðə ˌfedərəl ˌbjʊrəʊ əv ɪnˌvestɪˈɡeɪʃn/
(abbreviation FBI)
[singular]the police department in the US that is controlled by the national government and that is responsible for dealing with crimes that affect more than one state