He/She is a sandwich short of a picnic
形容某人不太聪明，缺乏常识或智力不足。
非正式场合，幽默或贬义地评价他人智力。
英文释义
The person is lacking intelligence.
例句
Don't expect him to solve the problem; he's a sandwich short of a picnic.
典故来源
源自野餐时食物不齐全的比喻，暗示缺少关键部分，引申为智力欠缺。