Wiktionary
playback singer
n. A singer whose songs are pre-recorded for use in films, especially in Bollywood musicals
Wikipedia
Playback singer
A playback singer is a singer whose singing is pre-recorded for use in movies. Playback singers record songs for soundtracks, and actors or actresses lip-sync the songs for cameras, while the actual singer does not appear on screen.
Usage examples of "playback singer".
I was Lata Mangeshkar the playback singer and Bubu the clown at the circus behind Civil Lines….