To halt one's work or other activity.
I think I'll knock off for the evening and go to bed.
To kill.
The mobsters hired the guy to knock off their enemies.
To remove, as a discount or estimate.
They agreed to knock off 20% of the price.
To rob.
They decided to knock off a liquor store downtown.
To make a copy of, as of a design.
They send people to the shows in Milan for "ideas", which means knocking off the designs they guess would sell.
To assign (an item) to a bidder at an auction, indicated by knocking on the counter.
To have sex with.
To accomplish hastily.
I knocked off a couple of quick sketches before the design meeting.
An imitation of something, particularly a well-known product, usually lower in quality and price than the original.
It's not a name-brand bag; it's just a cheap knockoff.
A device in a knitting machine to remove loops from the needles.