1. Someone who gives up a high office, formally or officially; especially, a royal throne: "The duke, by giving up his title, was seen by many as an abdicator; but he was happy to retire to the country because since his younger brother also chose to abdicate his position, they were referred to as the 'Brother Abdicators'."
2. Anyone who fails to fulfill a duty or responsibility: "The manager of the store was an abdicator of his duties."