Definitions

1. verb

to remove or replace a dub (a recording of music, especially a remix)

“The DJ had to undub the song to get back to the original version.”

2. verb

to remove or reduce the level of a sound, especially to make it inaudible

“The sound engineer had to undub the background noise from the recording.”

3. noun

a removed or replaced dub

“The undub was used as a reference for the final mix.”