An incorrect spelling of the word knackered. When refering to a person, being knackered is to be more exhausted than just being 'tired', but not as much as being 'fucked'. Refering to an object, it could be damaged, or broken.
1. "After kicking puppies up a steep hill for the last 3 hours, I'm really knackered!", said Billy.
2. "I'll have to wash my clothes round at your house, Billy knackered our machine by putting puppies in it again.", said Rita.