a person who is not loyal or stops being loyal to their own country, social class, beliefs, etc.背叛者,叛徒;卖国贼
The leaders of the rebellion were hanged as traitors.叛乱的首领被作为叛国者绞死了。
The Chinese Communist Party branded (= called) Mr Gorbachev "a traitor to socialism".中国共产党称戈尔巴乔夫先生为“社会主义的叛徒”。