Definition from Wiktionary, the free dictionary
Alternative forms 
- (US, Canada) A children's prank in which a doorbell of a house is rung, and then the pranksters run away before the occupants of the house open the door.
- knock-knock ginger (UK)
- A full list of other names for this prank can be found at Knock, Knock, Ginger on Wikipedia.Wikipedia:Knock, Knock, Ginger