Buy the rumour, sell the news

In trading, buy the rumour sell the news refers to a phenomenon where the news gets priced-in ahead of being announced, causing an asset to rise in value.

Then, as soon as the news hits the media, traders sell. The idea is that you make your gains when some positive piece of news about the asset you’re trading is still speculation or hasn’t caught the attention of the broader market yet, and you take your profits when everyone has finally been made aware of the news through its official announcement.