riff-raff
(esp 尤作 the riff-raff) n [U]
(derog 贬) ill-behaved people of the lowest social class; the rabble 下等社会的为非作歹者; 乌合之众
Don't bring any riff-raff into my house! 别把不三不四的人领到我家来!
As a great many people will be visiting the country, the government will be building new hotels, an immense stadium, and a new Olympic-standard swimming pool.