hang on to one's hat字面意思是“抓住自己的帽子”但口语中，常用来表示有特别惊人的消息，相当于：“告诉你个特大消息！”

【例句】
Hang on to your hat,Yingzi was eliminated from that show.
告诉你个特大消息，樱子在那挡节目中被淘汰了。

Hang on to your hat, Tom asked Linda to marry him last night.
告诉你个特大消息，Tom昨晚向Linda求婚了。