mentally defective
adjective old-fashioned or offensive uk/ˌmen.təl.i dɪˈfek.tɪv/ us/ˌmen.t̬əl.i dɪˈfek.tɪv/
有心理缺陷的，有智力缺陷的
If you say that someone is mentally defective, you mean that they have low mental abilities because their brain is damaged due to an accident or illness, or has been damaged since birth.