Range of ideas tolerated in public discourse
Overton
The Overton window is the range of subjects and arguments politically acceptable to the mainstream population at a given time.
It is also known as the window of discourse. The key to the concept is that the window changes over time; it can shift, shrink, or expand. It exemplifies "the slow evolution of societal values and norms".
Text adapted from Wikipedia, CC BY-SA 4.0.