/singk/ , Informal.
n. (used esp. in the phrases in sync and out of sync)
1. Also, synch /singk/ , synchronization: The picture and the soundtrack were out of sync.
2. harmony or harmonious relationship: Management wants to be in sync with the client's wishes.
v.i. , v.t.
3. to synchronize; harmonize.
[ 1930-35; shortened form ]