This phrase is worth noting precisely because it does not belong in this dictionary: it makes sense in a moral universe that has utterly vanished. The last "cad and bounder" died, perhaps, about 1947 (see London Daily Telegraph obituaries for further evidence).
Although they are appropriately linked, the precise meanings differ. A "cad" is one who does harm to a woman's honor or sense of self-worth as, for example, by taking her for a garden walk when he has no intention of marrying her. A "bounder" is a presumptious upstart, seemingly ignorant of, but perhaps merely indifferent to, fundamental norms of propriety.
You, sir, are a cad and a bounder.
A cad perhaps, but no bounder. My family goes back to William I.