lip-syncing

Translations
пение под фонограмму
имитация пения под фонограмму
движение губ в такт фонограмме
липсинк
синхронизация движений губ с фонограммой
Definitions
The act of silently moving your lips in time with prerecorded singing or speech to make it appear that you are performing live.
The synchronization of a person's visible lip movements with prerecorded dialogue or singing, especially in films, television, animation, or dubbing.
Words
lip

noun
губа
syncing

noun
синхронизация