Which term refers to the act of increasing in greatness or power?

The term that refers to the act of increasing in greatness or power is "aggrandize." This verb originates from the French word "aggrandir," which means to make greater or enhance one's status or wealth. In a broader context, aggrandizing can imply not just a physical increase in power or greatness but also the elevation of one’s reputation or importance, often through exaggeration or enhancement of achievements.

In contrast, the other terms do not share this meaning. "Probity" refers to integrity and high ethical standards, while "imprimatur" denotes official approval or sanction, often in a literary or publishing context. "Pulchritude," on the other hand, pertains to beauty or physical attractiveness. Therefore, "aggrandize" is the only word that aligns with the concept of increasing greatness or power.