1.VerbOn an early naval vessel or pirate ship: to be forced to walk off the end of a gangplank (a plank of wood extending outwards from the side of the vessel) and plunge into the ocean and drown, used as a method of killing.
2.VerbTo be forced to resign from a position in an organization.
"After he was caught selling company secrets, it’s not surprising they made him walk the plank."