- to add (a person or persons) to a group by vote of those already members
- to appoint as an associate
- to persuade or lure (an opponent) to join one's own system, party, etc.
- to make use of for one's own purposes; take over or adopt
Origin of co-optClassical Latin cooptare, to choose, elect from co- (var. of com-), with + optare, to choose: see option