回眸一笑：looking back at someon with a smile(usually it is uesed to describe women)
擦肩而过：to brush against someone
eg. I passed her in the street twice last week.
无所不谈：Talking about everything with someone, usually it describes an intimate relationship(like friends)
下不为例：It is like a kind of order—— it can not happen next time
惴惴不安：be anxious and fearful