A crown pusher combines the functions of a crown with those of a pusher in a single knob.
Although many monopusher chronographs have a pusher that is co-axial with the crown, a crown pusher is something else entirely. The crown (and stem) is the pusher. For example, in the Seiko 6139 movement, the crown is pressed to advance the date. Some other movements, including the Eterna-Matic, use a pull of the crown for this function. Very few movements have used this technology, which makes it easy to accidentally trigger a change.