A person who behaves disreputably or unethically; a cad or dishonorable person, especially in British usage.
From bound (to leap or move in bounds) plus -er; originally meant someone who bounds about, later became slang for an unscrupulous person.
A bounder was British slang insult that perfectly captures moral disgust—someone who breaks social bounds, hence they're a 'bounder' who doesn't stay within decent limits.
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