If you say that someone is a liar, you mean that they tell lies.
例句
He was a liar and a cheat...他曾坑蒙拐骗。'She seems at times an accomplished liar,' he said.“她有时像个撒谎高手,”他说。
英汉词典释义
n.
说谎者;撒谎者
She was wrongly labelled a liar.她被错误地扣上说谎者的帽子。She’s the biggest liar I’ve ever known.她是我所见到的最厉害的说谎大王。The greatest liars talk most of themselves.最爱自吹自擂的人是最大的说谎者。