If a crime is extraditable, the law says a person accused of that crime can be sent to another country to face a court there. Not every crime works this way. A small local offence may not be extraditable; a serious crime that two countries have agreed about usually is. It describes the crime, not the person: you say an extraditable offence, not really an extraditable man. It is a legal adjective, not everyday talk. You meet it in news about someone hiding abroad, and in arguments about whether a treaty covers this case.