Crook can refer to the following:

• Crooking is a verb to refer to the action of creating a bend or curve; for example, crooking a finger. A crook may be anything that is crooked thusly. Specifically, a crook is a tool with a crook in it, such as a shepherd's or bishop's staff.
• In music, a crook is a length of tubing used to change the pitch of a natural horn or other brass instrument; by removing one crook of a given length and replacing it with a crook of another, the entire pitch of the instrument would change. A crook is also the term for a bent or curved pipe that connects the reed to the instrument body on some double reed instruments; in American usage this is generally called a bocal.
• Crook is a slang term for a criminal or a person of questionable morality. Its most famous use in U.S. history came in a speech by president Richard Nixon, who while defending himself from the Watergate scandal proclaimed: "I am not a crook." The adjective crooked can refer to such persons or actions. This version of the term may also be archaically used as a verb in reference to becoming a criminal or causing another to become a criminal.
• In Australian slang, crook can be an adjective referring to poor quality, either physically or mentally.
• Crook, County Durham, England
• Crook , Cumbria, England
• Crook , Devon, England
• Crook, Colorado, United States of America.
• George Crook was an American general.