Which word refers to something of crucial importance?

The term that refers to something of crucial importance is "pivotal." This word signifies that a certain element plays a critical role in a larger context, often determining the outcome or success of a situation. For example, in a project, a pivotal moment could be a decision point that affects the overall direction of the work or the final results.

In contrast, the other terms do not convey the same sense of essential importance. "Pleasant" describes something agreeable or nice, but it does not imply urgency or necessity. "Pompous" refers to someone who has an inflated sense of their own importance, rather than something that is crucial. "Prevalent" indicates something that is widespread or common but does not imply that it is vital or central to a situation. Therefore, "pivotal" clearly stands out as the word denoting crucial importance.