Callback

Noun

 * 1) The return of a situation to a previous position or state.
 * 2) A return telephone or radio call; especially one made automatically to authenticate a logon to a computer network
 * 3) A product recall because of a defect or safety concern.
 * 4)  A function pointer passed to another function that the latter can call for notification purposes.
 * 5)  a follow-up audition (casting)
 * 6)  a joke which references an earlier joke in the same routine