1. In computer science, a storage device that serves as a buffer to maintain synchronization between devices transmitting at different rates: Jack's iPad seemed to be extremely slow in communicating the data to his computer, so he was told that the synchronizers weren't working like they should.
2. A device that shows whether two recurrent motions take place at the same time: The pilot checked his synchronizer in order to sync the propellers of his plane which had two engines.