Noun

1. A joke in the following form:

   "Knock knock."

   "Who's there?"

   (The teller of the joke says a name.)

   (The person to whom the joke isn't being told repeats the name, followed by "who?")

   (The teller of the joke says a pun based on the name.)

   Example:

   Knock knock.

   Who's there?

   Judith.

   Judith who?

   Judith like me becauthe I have a lithp? (ie, Do you dislike me because I have a lisp?)