To appoint or elect someone to a body by the existing members. The board decided to co-opt a new member to fill the vacant position.
To adopt or take over something, often inappropriately or without permission. The movement was co-opted by political groups with different agendas.
To neutralize or win over (a person or group) by assimilating them into an established system, organization, or authority. The ruling party tried to co-opt the student activists by offering them advisory positions.