"Off" means approximately "out of", or "from" / "away from".
He needs to stop leeching money off his parents.
(He needs to stop always asking his parents for money, getting money from his parents.)
Sometimes "of" is added.
He makes a living off of suing people.
(used, for example, here)
But this is more colloquial and more typical for AmE.
Basing myself off of my previous experience, I expected this meeting to last at least two hours.
(taking my previous experience as a starting point, I'm taking from it that my next experience will turn out to be X) [real-life example of usage here]
"The Good Fight" (TV show) is a spin-off of "The Good Wife".
"Spin-off" is a noun, but here the meaning of "off" is also present: We have taken a previous show, and from it, we made a sequel.