Someone who betrays, or reveals confidential information; a squealer or informer.(noun)
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Use "betrayer" in a sentence
"The fluid levels in the special bath that protected her betrayer from the dangers of hyperspace flight ebbed, then began plunging."
"_ I have not acquired that sort of good breeding, sir, which isn't founded on good sense; -- and when I call the betrayer of female innocence a bad character, the term, I think, is too true to be abusive."
"Instinctively Lenoir divined that his betrayer was the young"