Of two things, to be closely related or to go together well; see hand in hand.
Of two people, to hold hands.
To agree, be coordinated with, or complement well.
To cause (a set of files, data, or settings) on one computer or device to be (and try to remain) the same as on another.
To set (a clock or watch) to display the same time as another.
To coordinate or combine.
To occur at the same time or with coordinated timing.
To cause (video and audio) to play in a coordinated way.