Cad was a slang term for a rebellious person, particularly a male who misused a woman.
After witnessing young Jean-Luc Picard's 2327 treatment of Corlina (dating her and Penny at the same time), Q remarked that he didn't know Picard had been such a cad, a fact that impressed him. (TNG: "Tapestry")
In 2365, cad was one of the terms Data supplied as a synonym for rogue. (TNG: "The Outrageous Okona")