lip-sync       
 verb [ I or T ] (also lip-synch) uk/ˈlɪp.sɪŋk/ us/ˈlɪp.sɪŋk/
 (演员)假唱,对口型
Performers who lip-sync songs pretend to be singing them when in fact they are just moving their lips.
  They could lip-sync as well as the video stars of the 1980s. 他们可以像80年代的录像明星一样对口型。 
 Actors lip-synch the singing. 演员们对口型演唱。 
 - More examples
 - Actors both sing and lip-sync to familiar tunes.
 - As long as somebody looks great in their video and can lip-sync well, people don't care.
 - I just wish she hadn't lip-synched.
 
lip-sync       
noun [ U ] (also lip-synch) uk/ˈlɪp.sɪŋk/ us/ˈlɪp.sɪŋk/
 (演员)假唱,对口型
a practice in which performers pretend to be singing a song, when in fact they are just moving their lips
  Your whole body is involved in the lip-sync, not only the mouth. 你的整个身体都参与对口型表演,而不仅仅是嘴巴。 
 Who wants to join in the lip-synch contest? 谁想参加对口型比赛? 
 - More examples
 - There's a video of a group of soldiers performing a lip-sync of Lady Gaga's "Telephone."
 - Mock Rock is an annual on-campus lip-sync show.
 - I used to do a lip-synch imitation of Britney Spears.