to elect, appoint, or choose someone for some position, especially as an assistant, member, or colleague;
e.g. They plan to co-opt her as a member of the board of leaders.
(verb)
to bring or absorb someone/something into a group such as a culture or movement, or to take over something and use it, often without the right or authority to do so;
e.g. The movement was quick to co-opt more activists into its ranks. They tried to co-opt my work and claim it as their own.