Noun: hook (rod bent into a curved shape). Also refers to a fishing hook, and the boxing punch known in English as a hook.
Pictured is Kapteeni Koukku, or Captain Hook, from the Disney classic Peter Pan.
As an idiomatic expression, used in inessive, elative and illative similarly to English hooked , koukku can be used to mean “unable to resist or cease doing”: Olen koukussa Conan O’Brienin ohjelmaan.
Koukku is also slang for the police.