Footage recorded without sound but which is intended for use in a sound film; the appropriate noises are added later in production. If the footage involves an actor speaking and thus has to be dubbed, expect issues
the voice track.
The source of the initialism is debated; theories include "Motor Only Shot/Sync" (per TOW's article
), "Missing Optical Sound", "Motion Omit Sound" and "Mitt Out Sound
See also Looping Lines