1 : somewhat formal
a : to leave a place especially to start a journey
The group is scheduled to depart tomorrow at 8:00 a.m.
Our flight departs at 6:15 a.m.
The train departed (from the station) on time.
The train departed the station on time.
b [no object] : to leave a job or position
He is departing after 20 years with the company.
She is replacing the departing manager. [=the manager who is leaving that job]
2 [no object] : to change something or do something in a different way — usually + from
The river departs [=turns, deviates] from its original course a few miles downstream.
The actors were not allowed to depart from the script. [=they were not allowed to say anything that was not in the script]
The company's managers don't want to depart from an approach that has worked well in the past. [=they do not want to change their approach]