If you describe someone as a turncoat, you think they are disloyal or deceitful, because they have left their party or organization and joined an opposing one.
例句
His one-time admirers now accuse him of being a turncoat.曾经一度仰慕他的人如今指责他是叛徒。
英英词典释义
Noun
1. a disloyal person who betrays or deserts his cause or religion or political party or friend etc.