Flowback

Flowback can happen when a company in one country buys a company in a different country. If the buying company uses its shares as currency (buying the company with a share swap), the stockholders of the company getting sold receive a bunch of foreign shares as payment. They might not want the hassle of those foreign shares, so they sell the stock as soon as they get it.

This selling puts pressure on the buying company's shares in the immediate aftermath of the deal's closing.

Example.

Walmart buys a big-box retailer in Paraguay, Comprar Barato. It uses WMT shares to make the transaction. Now, there are a bunch of Paraguayans who formerly held shares in Comprar Barato who are sitting on a chunk of U.S.-listed WMT shares. They don't want to hold the foreign shares (maybe for tax reasons, maybe rules put forward by Paraguay's government...the specific reason doesn't matter). So, as soon as the deal closes, they dump their WMT stock. That move pushes down WMT's stock price.

Flowback...the shares are flowing back to U.S. ownership after the deal.