v.
     - strike a surface noisily to attract attention. 
▸strike or thump together or against something.
 ▸(of a motor) make a thumping or rattling noise.
 - collide forcefully with. 
▸force to move or fall with a blow or collision:
 he knocked over a glass of water.
  ▸injure or damage by striking.
 - make (a hole, dent, etc.) in something by striking it. 
▸bring into a specified condition by blows or rough treatment:
 two rooms had been knocked into one.
 - informal criticize.
 - 
(be knocking)
 Brit. informal be approaching (a specified age):
 he's knocking seventy.
 
n.
    - a sudden short sound caused by a blow. 
▸a continual thumping or rattling made by an engine.
 - a blow or collision.
 - a setback. 
▸informal a critical comment.
 - Cricket,  informal an innings.
 
 
  Phrase
  
    - knock it off
 informal stop doing something.  - knock someone on the head
 euphemistic kill someone.  - knock something on the head
 Brit. informal put an end to an idea, plan, etc.  - knock spots off
 Brit. informal easily outdo.  - the school of hard knocks
 painful or difficult but useful life experiences. 
   
  Phrase verbal
  
    - knock about 
(or around)
 informal  - spend time or travel without a specific purpose.
 - happen to be present.
 
  - knock something back
 informal consume a drink quickly.  - knock something down
   - (at an auction) confirm a sale by a knock with a hammer. 
▸informal reduce the price of an article.
 - US informal earn a specified sum as a wage.
 - Austral./NZ informal spend a pay cheque freely.
 
  - knock off
 informal stop work.  - knock someone off
  - informal kill someone.
 - Brit. vulgar slang have sex with a woman.
 
  - knock something off
   - informal produce a piece of work quickly and easily.
 - informal deduct an amount from a total.
 - Brit. informal steal something. 
▸N. Amer. informal rob a shop.
 ▸N. Amer. informal copy something illegally.
 
  - knock on
  - informal grow old.
 - 
(also knock the ball on)
 Rugby  illegally drive the ball with the hand or arm towards the opponents' goal line.
 
  - knock someone out
  - make someone unconscious. 
▸knock down (a boxer) for a count of ten.
 ▸informal astonish or greatly impress someone.
 - eliminate a competitor from a knockout competition.
 
  - knock something out
   - destroy or disable equipment.
 - informal produce work at a steady, fast rate.
 - Austral./NZ informal earn a specified sum of money.
 
  - knock something over
 N. Amer. informal rob a shop.  - knock someone sideways
 informal astonish someone.  - knock something together
 assemble something roughly and hastily.  - knock up
 Brit. informal (in a racket game) practise before play begins.  - knock someone up
  - Brit. awaken someone by knocking at their door.
 - informal, chiefly N. Amer. make a woman pregnant.
 
  - knock something up
  - Brit. make something hurriedly.
 - Cricket  score runs rapidly.
 
 
   
  Etymology
  OE cnocian, of imitative origin.