noun
Direct loan from English; used in casual or emphatic contexts to call someone a liar. Often carries a slightly stronger or more direct tone than native Japanese equivalents like 嘘つき.
彼はライアーだ。信じちゃダメ。
He's a liar. Don't believe him.
そんなのライアーの言い訳に過ぎないよ。
That's nothing but a liar's excuse.