Overdub – The process of adding additional tracks or sounds to a recording
To remember what overdub means, use the following mnemonic:
Her trainset was over double (overdub) the size of mine, and she's still adding additional tracks.
A simple example of overdubbing would be recording yourself singing over a karaoke song (no singing). There is very little modern music that is not built up (overdubbed) track by track, unless it's recorded live.