When you have a lengthy process after hiring someone, you call that the "onboarding" process. Is the term "offboarding" correct for a lengthy end-of-contract process? Or what would that be called?
The term "offboarding" refers to "Removing a user from an identity management system or downgrading the user's privileges." according to the Free Dictionary. I looked up the term on other websites, and they all concur. New York University even has an article titled "Offboarding Employees" where they discuss what to do when an employee leaves the company.
I hope this answers your question.
My organization uses the term "onboarding" and "offboarding". Onboarding I understand as it references the nautical term for boarding onto a ship but offboarding sounds wrong since you disembark from a ship. The term jettison suggested by @coleopterist seems like a reasonable nautical term to use when removing (somewhat forcefully) a person from a ship or organization.