knock knock

Noun

 * 1) A knock-knock joke

Interjection

 * 1)  A phrase used to introduce a "knock knock joke"
 * Knock knock./Who's there?/Wendy./Wendy who?/Wendy you want to open the door?
 * 1)  A phrase used in lieu of knocking (e.g. on the door), when it is not possible to knock.