mid-14c., "acting falsely," from un- (1) "not" + faithful. In Middle English it also had a sense of "infidel, unbelieving, irreligious" (late 14c.). Sense of "not faithful in marriage" is attested from 1828. Related: Unfaithfully; unfaithfulness.
权威例句
1. He vowed to wreak vengeance on his unfaithful, thieving wife.
他发誓要报复对自己不忠、爱偷东西的妻子。
2. Have you ever been unfaithful to him?
你对他是否有过不忠行为?
3. Have you ever been unfaithful to your wife?
你曾对妻子不忠 吗 ?
4. She wondered if Harry had been unfaithful to her during this long separation.
她不知道和哈里分开这么久,他是否曾对她不忠。
5. James had been unfaithful to Christine for the entire four years they'd been together.