The term "grand poobah" is often used to describe a person who holds a high position of authority or importance. However, there are several other words that can be used as synonyms for this phrase. Some of the most commonly used synonyms for grand poobah include "bigwig," "boss," "chief," "executive," "leader," "top dog," and "tycoon." Each of these words carries its own nuances and connotations, but they are all used to describe someone who holds a significant amount of power and influence within a particular organization or industry.