Riffraff (sometimes hyphenated—riff-raff) is a derogatory term for people the speaker considers socially inferior or undesirable. It’s a centuries-old term, having come to English from French around 1500. In modern use, the word is usually humorous or ironic. When used sincerely as a term for homeless or poor people (as in the final example below), it can make the writer sound stuck-up or insensitive.
The word has been spelled many ways through its history in English, but riffraff and riff-raff have been standard for a century or more, and both of those forms now appear throughout the English-speaking world (though the hyphenated form has the edge). Rift-raft is a misspelling.
Examples
It is the ghetto in which the riffraff or ‘dregs’ live their own life, isolated from the life of the rest of society. [Open Democracy]
The streets are clear of the usual riff-raff of the collegiate types, and the parties move out of homes and into offices. [Stark Exchange]
Des Moines cops. wandered stone-faced through a gaggle of frigid demonstrators while MSNBC host Joe Scarborough schmoozed with the riffraff. [Salon]
Dangerous abandoned properties become havens for bums and riff-raff and destroy local communities from the inside out. [KUSI]