off I .
1.
( informal ) to complete sth quickly and without much effort :
He knocks off three novels a year.
2.
( BrE , slang ) to steal sth; to steal from a place :
to knock off a video recorder
to knock off a bank
II .
knock sth off | ˌknock sth ↔ ˈoff sth
to reduce the price or value of sth :
They knocked off $60 because of a scratch.
The news knocked 13% off the company's shares.