She had come off in the cargo lighter, ...

[constantinusphilo]

She had come off in the cargo lighter, full of notabilities, sitting under the flutter of gay flags...
Nostromo by Joseph Conrad

The context shows that 'come off' is used in the meaning of 'departed, cast off' if I am correct.

 

[Rover_KE]

Without reading the book, there’s not enough context to be sure what it means.