knock down
phrasal verbknock somebody down (from something) (to something) 
- (informal) to persuade somebody to reduce the price of something- I managed to knock him down to $400.
 
knock somebody  down/over 
- to hit somebody and make them fall to the ground- She was knocked down by a bus.
- He knocked his opponent down three times in the first round.
 
knock something  down  
- to destroy a building by breaking its walls synonym demolish- These old houses are going to be knocked down.
 
knock something  down (from something) (to something) 
- (informal) to reduce the price of something- He knocked down the price from $80 to $50.