From MythTV Official Wiki
Process where video editing tools reverse the telecine process. Basically inverse telecine (or IVTC) brings back a movie's original framerate from NTSC's 29.97fps to 24fps.
What Is Telecine?
Gratuitously Stolen from Wikipedia:Telecine
Telecine (pronounced "tel-e-Sin-ee" or "tel-e-Sin-a" as 'cine' is the same root as in 'cinema') is the process of transferring motion picture film into electronic form, or the machine used in this process. Telecine enables a motion picture, captured originally on film, to be viewed with standard video equipment, such as televisions, video cassette decks or computers. This allows producers and distributors working in film to release their products on video and allows producers to use video production equipment to complete their film projects.