A man who has behaved in a morally wrong or socially shameful way — he cheats, he treats people badly, he pushes in where a decent man would not. It is a British word, and it belongs to another century’s drawing room. In old plays and novels a bounder is a cad: not a murderer, but someone you would not want your daughter to marry. Though actually, people who say it now often say it with a smile; it has gone old-fashioned and a bit comic, like cad and rotter. It is a word for a man, not a woman, and it is not current American English. The usual picture is a man who oversteps the bounds of decent behaviour. There is another idea, not proven, that it might echo a Hindi word for monkey which English picked up in India — treat that as a maybe, not a fact you must learn.

品行不端的男人、無賴（英國舊用語，現在聽來有點戲謔）