Is a feature of some modes of ventilation that allows the tidal volume to be delivered synchonised with the patient's breathing. Different ventilators do this differently; consult your ventilator manual for a detailed description of the synchronisation method used by your ventilator.
Figure 2. Synchronisation. The top figure represents a synchronous mode of ventilation where the Vt (blue) are delivered synchronised with the patient's respiratory effort (red arrows). The bottom figure represents a mode that is not synchronous with the same patient's respiratory effort (red arrows). Note: the same number of breaths are delivered during time depicted. The difference is that in the top figure the breaths are irregular, but synchronised with the patient's efforts, while in the bottom figure the breaths are regular, but not synchronised with the patient's efforts.
In general, a synchronised mode of ventilation is better tolerated by patients.