said of a committee or other body: to choose or elect (somebody) as a member
to take (e.g. a faction or movement) into a larger group; to assimilate
to take (something) and use it as one's own; to appropriate
co-optation /-ʹtaysh(ə)n/ noun
co-option /-sh(ə)n/ noun
co-optive /-tiv/ adj
[Latin cooptare, from co- + optare to choose]