Here are some possibilities of what you might be looking for:
* Chiefest: This is a valid word meaning "most important" or "principal." It's an archaic word used in formal or literary contexts.
* Chief: This is the more common word for the most important person in a group or organization, like a chief executive officer or the leader of a tribe.
* Chieftain: This refers to a leader of a tribe or clan, especially in historical contexts.
If you could provide more context, I might be able to help you understand what you're looking for. For example, tell me:
* Where did you see this word?
* What was the context of its usage?
* What are you trying to find out about this word?
With more information, I can give you a more accurate answer.