noun (n)

• the sound of knocking (as on a door or in an engine or bearing)

  suara ketukan (seperti di pintu atau di mesin atau bantalan)

  Example:
  The knocking grew louder.
  

  Synonym:
  knock
  

  source: wordnet30
• A beating; a rap; a series of raps.

  pemukulan; sebuah rap; serangkaian raps.

  source: webster1913