1. adjective - knackered
"You know what my love, I don't want to talk about it right now. I've been working all day, and I'm knackered. OK?"
2. adjective - knackered
Broken. Not working. In a state of disrepair.
"It's no good sweet-heart. I can't meet you today. The car's knackered."
Note: the word 'knacker' can also be used as a noun to denote, sometimes though not always in a derogatory manner, a tinker, a traveller, a travelling man. Eg. "Darling, the knackers have set up camp in the field round the corner!"