Wiktionary
n. A music video that combines lip-synching and audio dubbing
Wikipedia
A lip dub is a type of music video that combines lip synching and audio dubbing to make a music video. It is made by filming individuals or a group of people lip synching while listening to a song or any recorded audio then dubbing over it in post editing with the original audio of the song. There is often some form of mobile audio device used such as an MP3 player. Often they look like simple music videos, although many involve a lot of preparation and production. Lip dubs are usually done in a single unedited shot that often travel through different rooms and situations within a building. They have become popular with the advent of mass participatory video content sites like YouTube.