live in sin
未婚同居，指未結婚的情侶一起生活
口語·略帶幽默或傳統語境
英文釋義
to live together as a couple without being married
例句
They decided to live in sin for a few years before getting married.
典故來源
源自基督教傳統，將未婚同居視為違背教義的“罪惡”，20世紀后逐漸中性化。