The term used for the collective belief that the majority agrees on an issue, regardless of individual disagreement, is known as:

The concept you're referring to is most accurately captured by the term that relates to the collective belief in public opinion, regardless of individual opinions on the matter. The correct answer reflects a phenomenon where individuals mistakenly believe that their own views, or the views they hold, are widely shared by the majority, even if data or evidence suggests otherwise.

The choice of "Monounic Consensus" is intended to suggest a unified belief among the majority, but this is not a commonly recognized term in the context of public relations or social psychology. The terms "Dissensus" and "Pluralistic Ignorance" represent different concepts. Dissensus refers to disagreement or divergence of opinion within a group, which does not align with the notion of a perceived majority consensus. Pluralistic ignorance demonstrates a situation where a majority privately disagrees with a norm or belief but mistakenly believes that the majority holds a contrary view. False consensus is also a recognized psychological phenomenon but emphasizes the misbelief that one’s own preferences are the norm.

The answer that aligns best with the situation described in the question is the idea of a belief that the majority agrees on an issue, tapping into the false narrative that reinforces certain perceptions about social agreement.