Frameshift

In the context of politics and governance, the term "Overton Window" refers to a spectrum of thinkable, acceptable policies.

For most of American history, for instance, gay marriage was not supported by mainstream voters or politicians, and thus wasn't likely to happen; it was theoretically possible at any point in the country's existence, but until the early 2000s it just wasn't on most people's radars, and even for those who were aware of the possibility, it didn't seem prudent, likely, or desirable for various reasons.

That changed with the legalization of gay marriage in 2004 in Massachusetts, and that legalization sparked a process that culminated with legalization across the country in 2015.

This sort of movement—from unthinkable to thinkable to obvious—is an example of the Overton Window for this topic changing in the United States.