The term "crank" has several meanings, depending on its context.
1) In a general sense, it can refer to someone who is difficult or unpleasant to deal with, often due to their negative attitude or behavior. For example, "He's such a crank - always complaining about everything."
2) It can also mean an old-fashioned hand-cranked device, typically used for mechanical purposes. An example would be the cranking of an engine by turning the ignition key.
3) In some contexts, "crank" may refer to a drug user who is dependent on or addicted to drugs, particularly those that are injected intravenously. For instance, someone might say, “He’s such a crank – always looking for his next fix.”