DUB-IN
  1. any unknowingly created mental picture that appears to have been a record of the physical universe but is in fact only an altered copy of the time track. (HCOB 15 May 63)
  2. the phrase out of the motion picture industry of putting a sound track on top of something that isn't there . ( SH Spec 78, 6608C25)
  3. a recording which is being manufactured by a recording. (5811C07)
  4. imaginary recall—there is no pain dub-in. (DASF)

Technical Dictionary