lip flap noun2 •A failure in audio-video synchronization, so that an actor's lips move but no sound is heard. •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 formslip flaps
