ADR in film stands for “audio dialogue replacement”. If there was a sound issue regarding dialogue during production, ADR is used as a “re-do” for the actor to get his lines in. It’s tricky, and requires a lot of luck and precision to get just right. Here’s a four second video of LeDuc talking about money and stealing (what a criminal); the first one is before ADR (with bad production noise) and after with that nice clean ADR.
Film Before Visual ADR
Film After Visual ADR
ADR – re-recording audio to replace audio in shot.
partial ADR- match microphones, placement, and environmental reverb.
Visual ADR – actor visually matching lip sync.
audio ADR – actor matches the sound of original audio.