knocking

Etymology

verb

1. present participle and gerund of knock

noun

1. An act in which something is knocked on, or the sound thus produced
   These strange openings and closings and knockings were warnings and reminders from the spirits who attend the dying. 1893, W. B. Yeats, The Celtic Twilight
   There was no response to continued knockings. 1901, Carson Jay Lee, Oswald Langdon
   Recorded live to CD with new instrumentation--artillery shells, tuned suspension cables, boxes filled with springs--and deemphasized guitar parts, it's a beautiful collection of echoes and whispers, drones and knockings, with a gently swelling sense of the sinister. July 21, 2006, Keith Harris, Monica Kendrick, Peter Margasak, Bob Mehr, Miles Raymer, Neil Tesser, “The Treatment”, in Chicago Reader
2. (automotive) A repetitive ping, knock, or similar sound coming from an engine in which there are repeated uncontrolled explosions in the combustion chamber.
   Knocking can also occur at high speed, but that may go undetected by the driver. Dec 2021, The Road Ahead, Brisbane, page 56, column 1