Both Google and Microsoft Bing are testing hover effects that will bold elements of the search results. Google is testing bolding the description of the snippet and Bing is testing bolding the title of the snippet.
Both of these were spotted by Sachin Patel who posted videos of them.
He posted the Google one on X and wrote, "Google is testing a new treatment for descriptions—when users hover over them, they appear in bold."
Here is that GIF:
He posted the Bing one on X and wrote, "Bing is testing bold titles when hovering over them."
Here is that GIF:
Forum discussion at X.
