Knocking p. pr. & vb. n. : of Knock

Knocking n. : A beating; a rap; a series of raps.

Example:
What causes a Knocking sound from my driver's side tire?

Taxonomy
Joel P. Engardio, Knocking Documentary, Documentary Project, concentration camps, Jehovah's Witnesses, conservatives, Culture War, record number, court cases, freedom, blood transfusions, religious grounds, embrace, science, bloodless surgery, Nazi Germany, fight, Hitler.

Defination from the web:
KNOCKING ...