slang. Also nark. [Cf. Da. knark an old crabbed person.] a. A hard-hearted, unfeeling person. b. (See quot. 1873.)
1851. Mayhew, Lond. Labour, I. 315/1 (Hoppe). He was a good man; he couldn’t refuse a dog, much more a Christian; but he had a butler, a regular ‘knark.’
1873. Slang Dict., Nark, a person in the pay of the police; a common informer; one who gets his living by laying traps for publicans, &c.
