from
The Collaborative International Dictionary of English v.0.48
co-opt \co-opt"\, coopt \co*["o]pt"\, v. t. [See {Cooptate}. Cf.
F. coopter.]
To choose or elect in concert with another. [R.]
[1913 Webster]
Each of the hundred was to coopt three others. --Jowett
(Thucyd.).
[1913 Webster]
2. To choose or elect as a colleague or fellow member of a
group; as, The church members co-opted individuals from
similar backgrounds to replenish the congregation.
[PJC + WordNet 1.5]
3. To assimilate (a smaller group) into a larger group.
[PJC]
4. To persuade an opponent to join one's own side.
[PJC]
5. To appoint summarily (with or without the appointee's
consent).
[WordNet 1.5]
6. To appropriate (something rightly belonging to another) as
one's own; to preempt; as, to co-opt someone's name.
[PJC]