What is the meaning of knock?

noun

• The sound of knocking (as on a door or in an engine or bearing. )
  • usage: "the knocking grew louder"
  • synonyms: knocking
• Negative criticism.
  • synonyms: roast
• A vigorous blow.
  • usage: "the sudden knock floored him"; "he took a bash right in his face"; "he got a bang on the head"
  • synonyms: bash, bang, smash, belt
• A bad experience.
  • usage: "the school of hard knocks"
• The act of hitting vigorously.
  • usage: "he gave the table a whack"
  • synonyms: belt, rap, whack, whang

verb

• (v.) ()
  • synonyms: strike hard
• Rap with the knuckles.
  • usage: "knock on the door"
• Knock against with force or violence.
  • usage: "My car bumped into the tree"
  • synonyms: bump
• Make light, repeated taps on a surface.
  • usage: "he was tapping his fingers on the table impatiently"
  • synonyms: tap, rap, pink
• Sound like a car engine that is firing too early.
  • usage: "the car pinged when I put in low-octane gasoline"; "The car pinked when the ignition was too far retarded"
  • synonyms: pink, ping
• Find fault with; express criticism of; point out real or perceived flaws.
  • usage: "The paper criticized the new movie"; "Don't knock the food-it's free"
  • synonyms: criticize, criticise, pick apart