lip–synch or lip–sync 
/ˈlɪpˌsɪŋk/ verb
lip–synchs or lip–syncs; lip–synched or lip–synced; lip–synch·ing or lip–sync·ing /ˈlɪpˌsɪŋk/ verb : to pretend to sing or say (recorded words) [+ obj] ▪ He lip-synched the song that was playing on the radio. [no obj] ▪ He lip-synched to the song. ▪ It was obvious that he was lip-synching.
