lip flap

Noun

lip flap (countable and uncountable, plural lip flaps)

1. A failure in audio-video synchronization, so that an actor's lips move but no sound is heard.
2. A movement of an actor's lips, which is to be matched as closely as possible in a dubbed version of the film.
   • […] pick it up earlier or later where there is no lip-flap. But if you must take it there, then you must precede it with another shot of the same speaker at a different angle, hopefully closer.1972, Filmmakers Newsletter, volume 5, number 7, part 12, page 46
   • “So when we translate,” Lam was saying, “it's all about what we call lip flaps. Like, how many times does mouth move? We match translation more to mouth than to what words really mean.2009, Shawn Klomparens, Two Years, No Rain, page 49
3. Used other than figuratively or idiomatically: see lip, flap.