I. sync¹ , synch /sɪŋk/ noun
[Date: 1900-2000; Origin: synchronization]

1. in sync (with something/somebody)
a) if things are in sync, they are working well together at exactly the same time and speed
be/move/work in sync
The two mechanisms have to work in sync.
The soundtrack is not quite in sync with the picture.
b) matching or in agreement:
a celebrity who is in sync with young people’s lifestyles
The President is in sync with Thompson’s views on many issues.

2. out of sync (with something/somebody)
a) if things are out of sync, they are not working well together at exactly the same time and speed
b) not matching or not in agreement

[TahlilGaran] Dictionary of Contemporary English ▲

II. sync² , synch (also sync something ↔ up) verb [intransitive and transitive]
to arrange for two or more things to happen at exactly the same time, or to happen at the same time or in the same way as something else Synonym : synchronize:
The hardest part was syncing the music to the video.
Wait for the computer to synch up with your command.

[TahlilGaran] Dictionary of Contemporary English ▲