一笑而过,literally means laugh it off. It is a phrase describing someone who has open, generous and optimistic attitudes towards adverse situation.e.g. 面对这些流言蜚语,她只是一笑而过。 However, in other cases, such as the lyrics, "你伤害了我,还一笑而过“, it shows the attitude of "being indifferent" or "does not care". " You hurt me, but you just laughed it off."